diff --git a/_sass/_bootstrap-variables.scss b/_sass/_bootstrap-variables.scss
index 6824794..df520cb 100755
--- a/_sass/_bootstrap-variables.scss
+++ b/_sass/_bootstrap-variables.scss
@@ -1,3 +1,5 @@
+// assets/css/style.scss is where Jekyll loads the main stylesheet
+
 $grid-breakpoints: (
   xs: 0,
   sm: 576px,
diff --git a/_sass/bootstrap/_alert.scss b/_sass/bootstrap/_alert.scss
index da2a98a..4aa1fc2 100644
--- a/_sass/bootstrap/_alert.scss
+++ b/_sass/bootstrap/_alert.scss
@@ -34,6 +34,7 @@
     position: absolute;
     top: 0;
     right: 0;
+    z-index: 2;
     padding: $alert-padding-y $alert-padding-x;
     color: inherit;
   }
diff --git a/_sass/bootstrap/_breadcrumb.scss b/_sass/bootstrap/_breadcrumb.scss
index d748894..9c204c7 100644
--- a/_sass/bootstrap/_breadcrumb.scss
+++ b/_sass/bootstrap/_breadcrumb.scss
@@ -15,7 +15,7 @@
     padding-left: $breadcrumb-item-padding;
 
     &::before {
-      display: inline-block; // Suppress underlining of the separator in modern browsers
+      float: left; // Suppress inline spacings and underlining of the separator
       padding-right: $breadcrumb-item-padding;
       color: $breadcrumb-divider-color;
       content: escape-svg($breadcrumb-divider);
diff --git a/_sass/bootstrap/_buttons.scss b/_sass/bootstrap/_buttons.scss
index e87d339..6ee24ba 100644
--- a/_sass/bootstrap/_buttons.scss
+++ b/_sass/bootstrap/_buttons.scss
@@ -10,9 +10,9 @@
   font-weight: $btn-font-weight;
   color: $body-color;
   text-align: center;
+  text-decoration: if($link-decoration == none, null, none);
   white-space: $btn-white-space;
   vertical-align: middle;
-  cursor: if($enable-pointer-cursor-for-buttons, pointer, null);
   user-select: none;
   background-color: transparent;
   border: $btn-border-width solid transparent;
@@ -37,12 +37,16 @@
     @include box-shadow(none);
   }
 
-  &:not(:disabled):not(.disabled):active,
-  &:not(:disabled):not(.disabled).active {
-    @include box-shadow($btn-active-box-shadow);
+  &:not(:disabled):not(.disabled) {
+    cursor: if($enable-pointer-cursor-for-buttons, pointer, null);
 
-    &:focus {
-      @include box-shadow($btn-focus-box-shadow, $btn-active-box-shadow);
+    &:active,
+    &.active {
+      @include box-shadow($btn-active-box-shadow);
+
+      &:focus {
+        @include box-shadow($btn-focus-box-shadow, $btn-active-box-shadow);
+      }
     }
   }
 }
@@ -89,7 +93,6 @@ fieldset:disabled a.btn {
   &:focus,
   &.focus {
     text-decoration: $link-hover-decoration;
-    box-shadow: none;
   }
 
   &:disabled,
diff --git a/_sass/bootstrap/_card.scss b/_sass/bootstrap/_card.scss
index d6759fd..faaa75e 100644
--- a/_sass/bootstrap/_card.scss
+++ b/_sass/bootstrap/_card.scss
@@ -19,16 +19,26 @@
     margin-left: 0;
   }
 
-  > .list-group:first-child {
-    .list-group-item:first-child {
-      @include border-top-radius($card-border-radius);
+  > .list-group {
+    border-top: inherit;
+    border-bottom: inherit;
+
+    &:first-child {
+      border-top-width: 0;
+      @include border-top-radius($card-inner-border-radius);
+    }
+
+    &:last-child  {
+      border-bottom-width: 0;
+      @include border-bottom-radius($card-inner-border-radius);
     }
   }
 
-  > .list-group:last-child {
-    .list-group-item:last-child {
-      @include border-bottom-radius($card-border-radius);
-    }
+  // Due to specificity of the above selector (`.card > .list-group`), we must
+  // use a child selector here to prevent double borders.
+  > .card-header + .list-group,
+  > .list-group + .card-footer {
+    border-top: 0;
   }
 }
 
@@ -80,16 +90,11 @@
   &:first-child {
     @include border-radius($card-inner-border-radius $card-inner-border-radius 0 0);
   }
-
-  + .list-group {
-    .list-group-item:first-child {
-      border-top: 0;
-    }
-  }
 }
 
 .card-footer {
   padding: $card-spacer-y $card-spacer-x;
+  color: $card-cap-color;
   background-color: $card-cap-bg;
   border-top: $card-border-width solid $card-border-color;
 
@@ -123,6 +128,7 @@
   bottom: 0;
   left: 0;
   padding: $card-img-overlay-padding;
+  @include border-radius($card-inner-border-radius);
 }
 
 .card-img,
@@ -200,12 +206,12 @@
 
           .card-img-top,
           .card-header {
-            // stylelint-disable-next-line property-blacklist
+            // stylelint-disable-next-line property-disallowed-list
             border-top-right-radius: 0;
           }
           .card-img-bottom,
           .card-footer {
-            // stylelint-disable-next-line property-blacklist
+            // stylelint-disable-next-line property-disallowed-list
             border-bottom-right-radius: 0;
           }
         }
@@ -215,12 +221,12 @@
 
           .card-img-top,
           .card-header {
-            // stylelint-disable-next-line property-blacklist
+            // stylelint-disable-next-line property-disallowed-list
             border-top-left-radius: 0;
           }
           .card-img-bottom,
           .card-footer {
-            // stylelint-disable-next-line property-blacklist
+            // stylelint-disable-next-line property-disallowed-list
             border-bottom-left-radius: 0;
           }
         }
@@ -258,6 +264,8 @@
 //
 
 .accordion {
+  overflow-anchor: none;
+
   > .card {
     overflow: hidden;
 
diff --git a/_sass/bootstrap/_carousel.scss b/_sass/bootstrap/_carousel.scss
index fb5e9f8..db30bed 100644
--- a/_sass/bootstrap/_carousel.scss
+++ b/_sass/bootstrap/_carousel.scss
@@ -127,7 +127,7 @@
   display: inline-block;
   width: $carousel-control-icon-width;
   height: $carousel-control-icon-width;
-  background: no-repeat 50% / 100% 100%;
+  background: 50% / 100% 100% no-repeat;
 }
 .carousel-control-prev-icon {
   background-image: escape-svg($carousel-control-prev-icon-bg);
diff --git a/_sass/bootstrap/_close.scss b/_sass/bootstrap/_close.scss
index 071aebe..82e9593 100644
--- a/_sass/bootstrap/_close.scss
+++ b/_sass/bootstrap/_close.scss
@@ -30,7 +30,6 @@ button.close {
   padding: 0;
   background-color: transparent;
   border: 0;
-  appearance: none;
 }
 
 // Future-proof disabling of clicks on `<a>` elements
diff --git a/_sass/bootstrap/_custom-forms.scss b/_sass/bootstrap/_custom-forms.scss
index 21e72da..06725ff 100644
--- a/_sass/bootstrap/_custom-forms.scss
+++ b/_sass/bootstrap/_custom-forms.scss
@@ -9,9 +9,11 @@
 
 .custom-control {
   position: relative;
+  z-index: 1;
   display: block;
   min-height: $font-size-base * $line-height-base;
   padding-left: $custom-control-gutter + $custom-control-indicator-size;
+  color-adjust: exact; // Keep themed appearance for print
 }
 
 .custom-control-inline {
@@ -37,7 +39,7 @@
   &:focus ~ .custom-control-label::before {
     // the mixin is not used here to make sure there is feedback
     @if $enable-shadows {
-      box-shadow: $input-box-shadow, $input-focus-box-shadow;
+      box-shadow: $input-box-shadow, $custom-control-indicator-focus-box-shadow;
     } @else {
       box-shadow: $custom-control-indicator-focus-box-shadow;
     }
@@ -102,7 +104,7 @@
     width: $custom-control-indicator-size;
     height: $custom-control-indicator-size;
     content: "";
-    background: no-repeat 50% / #{$custom-control-indicator-bg-size};
+    background: 50% / #{$custom-control-indicator-bg-size} no-repeat;
   }
 }
 
@@ -135,10 +137,10 @@
 
   .custom-control-input:disabled {
     &:checked ~ .custom-control-label::before {
-      background-color: $custom-control-indicator-checked-disabled-bg;
+      @include gradient-bg($custom-control-indicator-checked-disabled-bg);
     }
     &:indeterminate ~ .custom-control-label::before {
-      background-color: $custom-control-indicator-checked-disabled-bg;
+      @include gradient-bg($custom-control-indicator-checked-disabled-bg);
     }
   }
 }
@@ -149,7 +151,7 @@
 
 .custom-radio {
   .custom-control-label::before {
-    // stylelint-disable-next-line property-blacklist
+    // stylelint-disable-next-line property-disallowed-list
     border-radius: $custom-radio-indicator-border-radius;
   }
 
@@ -161,7 +163,7 @@
 
   .custom-control-input:disabled {
     &:checked ~ .custom-control-label::before {
-      background-color: $custom-control-indicator-checked-disabled-bg;
+      @include gradient-bg($custom-control-indicator-checked-disabled-bg);
     }
   }
 }
@@ -179,7 +181,7 @@
       left: -($custom-switch-width + $custom-control-gutter);
       width: $custom-switch-width;
       pointer-events: all;
-      // stylelint-disable-next-line property-blacklist
+      // stylelint-disable-next-line property-disallowed-list
       border-radius: $custom-switch-indicator-border-radius;
     }
 
@@ -189,7 +191,7 @@
       width: $custom-switch-indicator-size;
       height: $custom-switch-indicator-size;
       background-color: $custom-control-indicator-border-color;
-      // stylelint-disable-next-line property-blacklist
+      // stylelint-disable-next-line property-disallowed-list
       border-radius: $custom-switch-indicator-border-radius;
       @include transition(transform .15s ease-in-out, $custom-forms-transition);
     }
@@ -204,7 +206,7 @@
 
   .custom-control-input:disabled {
     &:checked ~ .custom-control-label::before {
-      background-color: $custom-control-indicator-checked-disabled-bg;
+      @include gradient-bg($custom-control-indicator-checked-disabled-bg);
     }
   }
 }
@@ -237,8 +239,9 @@
     border-color: $custom-select-focus-border-color;
     outline: 0;
     @if $enable-shadows {
-      box-shadow: $custom-select-box-shadow, $custom-select-focus-box-shadow;
+      @include box-shadow($custom-select-box-shadow, $custom-select-focus-box-shadow);
     } @else {
+      // Avoid using mixin so we can pass custom focus shadow properly
       box-shadow: $custom-select-focus-box-shadow;
     }
 
@@ -312,6 +315,7 @@
   width: 100%;
   height: $custom-file-height;
   margin: 0;
+  overflow: hidden;
   opacity: 0;
 
   &:focus ~ .custom-file-label {
@@ -344,6 +348,7 @@
   z-index: 1;
   height: $custom-file-height;
   padding: $custom-file-padding-y $custom-file-padding-x;
+  overflow: hidden;
   font-family: $custom-file-font-family;
   font-weight: $custom-file-font-weight;
   line-height: $custom-file-line-height;
@@ -385,7 +390,7 @@
   appearance: none;
 
   &:focus {
-    outline: none;
+    outline: 0;
 
     // Pseudo-elements must be split across multiple rulesets to have an effect.
     // No box-shadow() mixin for focus accessibility.
diff --git a/_sass/bootstrap/_dropdown.scss b/_sass/bootstrap/_dropdown.scss
index 76f33a4..f39de11 100644
--- a/_sass/bootstrap/_dropdown.scss
+++ b/_sass/bootstrap/_dropdown.scss
@@ -22,7 +22,7 @@
   display: none; // none by default, but block on "open" of the menu
   float: left;
   min-width: $dropdown-min-width;
-  padding: $dropdown-padding-y 0;
+  padding: $dropdown-padding-y $dropdown-padding-x;
   margin: $dropdown-spacer 0 0; // override default ul
   @include font-size($dropdown-font-size);
   color: $dropdown-color;
@@ -100,7 +100,7 @@
   }
 }
 
-// When enabled Popper.js, reset basic dropdown position
+// When Popper is enabled, reset the basic dropdown position
 // stylelint-disable-next-line no-duplicate-selectors
 .dropdown-menu {
   &[x-placement^="top"],
@@ -128,6 +128,7 @@
   font-weight: $font-weight-normal;
   color: $dropdown-link-color;
   text-align: inherit; // For `<button>`s
+  text-decoration: if($link-decoration == none, null, none);
   white-space: nowrap; // prevent links from randomly breaking onto new lines
   background-color: transparent; // For `<button>`s
   border: 0; // For `<button>`s
@@ -176,7 +177,7 @@
 // Dropdown section headers
 .dropdown-header {
   display: block;
-  padding: $dropdown-padding-y $dropdown-item-padding-x;
+  padding: $dropdown-header-padding;
   margin-bottom: 0; // for use with heading elements
   @include font-size($font-size-sm);
   color: $dropdown-header-color;
diff --git a/_sass/bootstrap/_forms.scss b/_sass/bootstrap/_forms.scss
index b2edb7b..66a4efe 100644
--- a/_sass/bootstrap/_forms.scss
+++ b/_sass/bootstrap/_forms.scss
@@ -59,6 +59,15 @@
   }
 }
 
+input[type="date"],
+input[type="time"],
+input[type="datetime-local"],
+input[type="month"] {
+  &.form-control {
+    appearance: none; // Fix appearance for date inputs in Safari
+  }
+}
+
 select.form-control {
   &:focus::-ms-value {
     // Suppress the nested default white text on blue background highlight given to
diff --git a/_sass/bootstrap/_functions.scss b/_sass/bootstrap/_functions.scss
index 695e6cd..9c06603 100644
--- a/_sass/bootstrap/_functions.scss
+++ b/_sass/bootstrap/_functions.scss
@@ -23,10 +23,12 @@
 // Starts at zero
 // Used to ensure the min-width of the lowest breakpoint starts at 0.
 @mixin _assert-starts-at-zero($map, $map-name: "$grid-breakpoints") {
-  $values: map-values($map);
-  $first-value: nth($values, 1);
-  @if $first-value != 0 {
-    @warn "First breakpoint in #{$map-name} must start at 0, but starts at #{$first-value}.";
+  @if length($map) > 0 {
+    $values: map-values($map);
+    $first-value: nth($values, 1);
+    @if $first-value != 0 {
+      @warn "First breakpoint in #{$map-name} must start at 0, but starts at #{$first-value}.";
+    }
   }
 }
 
@@ -49,10 +51,18 @@
 }
 
 // See https://codepen.io/kevinweber/pen/dXWoRw
+//
+// Requires the use of quotes around data URIs.
+
 @function escape-svg($string) {
   @if str-index($string, "data:image/svg+xml") {
     @each $char, $encoded in $escaped-characters {
-      $string: str-replace($string, $char, $encoded);
+      // Do not escape the url brackets
+      @if str-index($string, "url(") == 1 {
+        $string: url("#{str-replace(str-slice($string, 6, -3), $char, $encoded)}");
+      } @else {
+        $string: str-replace($string, $char, $encoded);
+      }
     }
   }
 
diff --git a/_sass/bootstrap/_grid.scss b/_sass/bootstrap/_grid.scss
index d36ee75..0bfe530 100644
--- a/_sass/bootstrap/_grid.scss
+++ b/_sass/bootstrap/_grid.scss
@@ -4,11 +4,7 @@
 
 @if $enable-grid-classes {
   // Single container class with breakpoint max-widths
-  .container {
-    @include make-container();
-    @include make-container-max-widths();
-  }
-
+  .container,
   // 100% wide container at all breakpoints
   .container-fluid {
     @include make-container();
@@ -25,11 +21,19 @@
         max-width: $container-max-width;
       }
 
+      // Extend each breakpoint which is smaller or equal to the current breakpoint
+      $extend-breakpoint: true;
+
       @each $name, $width in $grid-breakpoints {
-        @if ($container-max-width > $width or $breakpoint == $name) {
+        @if ($extend-breakpoint) {
           .container#{breakpoint-infix($name, $grid-breakpoints)} {
             @extend %responsive-container-#{$breakpoint};
           }
+
+          // Once the current breakpoint is reached, stop extending
+          @if ($breakpoint == $name) {
+            $extend-breakpoint: false;
+          }
         }
       }
     }
diff --git a/_sass/bootstrap/_input-group.scss b/_sass/bootstrap/_input-group.scss
index bf69ddb..d72ebea 100644
--- a/_sass/bootstrap/_input-group.scss
+++ b/_sass/bootstrap/_input-group.scss
@@ -16,7 +16,8 @@
   > .custom-select,
   > .custom-file {
     position: relative; // For focus state's z-index
-    flex: 1 1 0%;
+    flex: 1 1 auto;
+    width: 1%;
     min-width: 0; // https://stackoverflow.com/questions/36247140/why-dont-flex-items-shrink-past-content-size
     margin-bottom: 0;
 
@@ -41,7 +42,6 @@
 
   > .form-control,
   > .custom-select {
-    &:not(:last-child) { @include border-right-radius(0); }
     &:not(:first-child) { @include border-left-radius(0); }
   }
 
@@ -52,9 +52,24 @@
     align-items: center;
 
     &:not(:last-child) .custom-file-label,
-    &:not(:last-child) .custom-file-label::after { @include border-right-radius(0); }
     &:not(:first-child) .custom-file-label { @include border-left-radius(0); }
   }
+
+  &:not(.has-validation) {
+    > .form-control:not(:last-child),
+    > .custom-select:not(:last-child),
+    > .custom-file:not(:last-child) .custom-file-label::after {
+      @include border-right-radius(0);
+    }
+  }
+
+  &.has-validation {
+    > .form-control:nth-last-child(n + 3),
+    > .custom-select:nth-last-child(n + 3),
+    > .custom-file:nth-last-child(n + 3) .custom-file-label::after {
+      @include border-right-radius(0);
+    }
+  }
 }
 
 
@@ -174,8 +189,10 @@
 
 .input-group > .input-group-prepend > .btn,
 .input-group > .input-group-prepend > .input-group-text,
-.input-group > .input-group-append:not(:last-child) > .btn,
-.input-group > .input-group-append:not(:last-child) > .input-group-text,
+.input-group:not(.has-validation) > .input-group-append:not(:last-child) > .btn,
+.input-group:not(.has-validation) > .input-group-append:not(:last-child) > .input-group-text,
+.input-group.has-validation > .input-group-append:nth-last-child(n + 3) > .btn,
+.input-group.has-validation > .input-group-append:nth-last-child(n + 3) > .input-group-text,
 .input-group > .input-group-append:last-child > .btn:not(:last-child):not(.dropdown-toggle),
 .input-group > .input-group-append:last-child > .input-group-text:not(:last-child) {
   @include border-right-radius(0);
diff --git a/_sass/bootstrap/_list-group.scss b/_sass/bootstrap/_list-group.scss
index 468c2e3..ec25ba8 100644
--- a/_sass/bootstrap/_list-group.scss
+++ b/_sass/bootstrap/_list-group.scss
@@ -9,6 +9,7 @@
   // No need to set list-style: none; since .list-group-item is block level
   padding-left: 0; // reset padding because ul and ol
   margin-bottom: 0;
+  @include border-radius($list-group-border-radius);
 }
 
 
@@ -46,15 +47,16 @@
   display: block;
   padding: $list-group-item-padding-y $list-group-item-padding-x;
   color: $list-group-color;
+  text-decoration: if($link-decoration == none, null, none);
   background-color: $list-group-bg;
   border: $list-group-border-width solid $list-group-border-color;
 
   &:first-child {
-    @include border-top-radius($list-group-border-radius);
+    @include border-top-radius(inherit);
   }
 
   &:last-child {
-    @include border-bottom-radius($list-group-border-radius);
+    @include border-bottom-radius(inherit);
   }
 
   &.disabled,
@@ -94,7 +96,7 @@
     .list-group-horizontal#{$infix} {
       flex-direction: row;
 
-      .list-group-item {
+      > .list-group-item {
         &:first-child {
           @include border-bottom-left-radius($list-group-border-radius);
           @include border-top-right-radius(0);
@@ -109,7 +111,7 @@
           margin-top: 0;
         }
 
-        & + .list-group-item {
+        + .list-group-item {
           border-top-width: $list-group-border-width;
           border-left-width: 0;
 
@@ -130,18 +132,12 @@
 // useful within other components (e.g., cards).
 
 .list-group-flush {
-  .list-group-item {
-    border-right-width: 0;
-    border-left-width: 0;
-    @include border-radius(0);
+  @include border-radius(0);
 
-    &:first-child {
-      border-top-width: 0;
-    }
-  }
+  > .list-group-item {
+    border-width: 0 0 $list-group-border-width;
 
-  &:last-child {
-    .list-group-item:last-child {
+    &:last-child {
       border-bottom-width: 0;
     }
   }
diff --git a/_sass/bootstrap/_modal.scss b/_sass/bootstrap/_modal.scss
index 9053c17..e43c70f 100644
--- a/_sass/bootstrap/_modal.scss
+++ b/_sass/bootstrap/_modal.scss
@@ -83,6 +83,7 @@
   &::before {
     display: block; // IE10
     height: subtract(100vh, $modal-dialog-margin * 2);
+    height: min-content; // Reset height to 0 except on IE
     content: "";
   }
 
@@ -181,7 +182,6 @@
   // Place margin between footer elements
   // This solution is far from ideal because of the universal selector usage,
   // but is needed to fix https://github.com/twbs/bootstrap/issues/24800
-  // stylelint-disable-next-line selector-max-universal
   > * {
     margin: $modal-footer-margin-between / 2;
   }
@@ -217,6 +217,7 @@
 
     &::before {
       height: subtract(100vh, $modal-dialog-margin-y-sm-up * 2);
+      height: min-content;
     }
   }
 
diff --git a/_sass/bootstrap/_nav.scss b/_sass/bootstrap/_nav.scss
index 667d682..fad684e 100644
--- a/_sass/bootstrap/_nav.scss
+++ b/_sass/bootstrap/_nav.scss
@@ -14,6 +14,7 @@
 .nav-link {
   display: block;
   padding: $nav-link-padding-y $nav-link-padding-x;
+  text-decoration: if($link-decoration == none, null, none);
 
   @include hover-focus() {
     text-decoration: none;
@@ -34,11 +35,8 @@
 .nav-tabs {
   border-bottom: $nav-tabs-border-width solid $nav-tabs-border-color;
 
-  .nav-item {
-    margin-bottom: -$nav-tabs-border-width;
-  }
-
   .nav-link {
+    margin-bottom: -$nav-tabs-border-width;
     border: $nav-tabs-border-width solid transparent;
     @include border-top-radius($nav-tabs-border-radius);
 
@@ -91,6 +89,7 @@
 //
 
 .nav-fill {
+  > .nav-link,
   .nav-item {
     flex: 1 1 auto;
     text-align: center;
@@ -98,6 +97,7 @@
 }
 
 .nav-justified {
+  > .nav-link,
   .nav-item {
     flex-basis: 0;
     flex-grow: 1;
diff --git a/_sass/bootstrap/_navbar.scss b/_sass/bootstrap/_navbar.scss
index 5f10a62..cf5b667 100644
--- a/_sass/bootstrap/_navbar.scss
+++ b/_sass/bootstrap/_navbar.scss
@@ -136,8 +136,12 @@
   height: 1.5em;
   vertical-align: middle;
   content: "";
-  background: no-repeat center center;
-  background-size: 100% 100%;
+  background: 50% / 100% 100% no-repeat;
+}
+
+.navbar-nav-scroll {
+  max-height: $navbar-nav-scroll-max-height;
+  overflow-y: auto;
 }
 
 // Generate series of `.navbar-expand-*` responsive classes for configuring
@@ -199,6 +203,10 @@
           }
         }
 
+        .navbar-nav-scroll {
+          overflow: visible;
+        }
+
         .navbar-collapse {
           display: flex !important; // stylelint-disable-line declaration-no-important
 
diff --git a/_sass/bootstrap/_pagination.scss b/_sass/bootstrap/_pagination.scss
index 953a35a..9313cc5 100644
--- a/_sass/bootstrap/_pagination.scss
+++ b/_sass/bootstrap/_pagination.scss
@@ -11,6 +11,7 @@
   margin-left: -$pagination-border-width;
   line-height: $pagination-line-height;
   color: $pagination-color;
+  text-decoration: if($link-decoration == none, null, none);
   background-color: $pagination-bg;
   border: $pagination-border-width solid $pagination-border-color;
 
@@ -65,9 +66,9 @@
 //
 
 .pagination-lg {
-  @include pagination-size($pagination-padding-y-lg, $pagination-padding-x-lg, $font-size-lg, $line-height-lg, $border-radius-lg);
+  @include pagination-size($pagination-padding-y-lg, $pagination-padding-x-lg, $font-size-lg, $line-height-lg, $pagination-border-radius-lg);
 }
 
 .pagination-sm {
-  @include pagination-size($pagination-padding-y-sm, $pagination-padding-x-sm, $font-size-sm, $line-height-sm, $border-radius-sm);
+  @include pagination-size($pagination-padding-y-sm, $pagination-padding-x-sm, $font-size-sm, $line-height-sm, $pagination-border-radius-sm);
 }
diff --git a/_sass/bootstrap/_progress.scss b/_sass/bootstrap/_progress.scss
index 37ef602..e206474 100644
--- a/_sass/bootstrap/_progress.scss
+++ b/_sass/bootstrap/_progress.scss
@@ -10,6 +10,7 @@
   display: flex;
   height: $progress-height;
   overflow: hidden; // force rounded corners by cropping it
+  line-height: 0;
   @include font-size($progress-font-size);
   background-color: $progress-bg;
   @include border-radius($progress-border-radius);
@@ -35,7 +36,7 @@
 
 @if $enable-transitions {
   .progress-bar-animated {
-    animation: progress-bar-stripes $progress-bar-animation-timing;
+    animation: $progress-bar-animation-timing progress-bar-stripes;
 
     @if $enable-prefers-reduced-motion-media-query {
       @media (prefers-reduced-motion: reduce) {
diff --git a/_sass/bootstrap/_reboot.scss b/_sass/bootstrap/_reboot.scss
index b6c98cc..cd93bfe 100644
--- a/_sass/bootstrap/_reboot.scss
+++ b/_sass/bootstrap/_reboot.scss
@@ -1,4 +1,4 @@
-// stylelint-disable at-rule-no-vendor-prefix, declaration-no-important, selector-no-qualifying-type, property-no-vendor-prefix
+// stylelint-disable declaration-no-important, selector-no-qualifying-type, property-no-vendor-prefix
 
 // Reboot
 //
@@ -199,7 +199,7 @@ a {
 // causes specificity issues in many other styles that are too complex to fix.
 // See https://github.com/twbs/bootstrap/issues/19402
 
-a:not([href]) {
+a:not([href]):not([class]) {
   color: inherit;
   text-decoration: none;
 
@@ -229,6 +229,9 @@ pre {
   margin-bottom: 1rem;
   // Don't allow content to break outside
   overflow: auto;
+  // Disable auto-hiding scrollbar in IE & legacy Edge to avoid overlap,
+  // making it impossible to interact with the content
+  -ms-overflow-style: scrollbar;
 }
 
 
@@ -275,10 +278,14 @@ caption {
   caption-side: bottom;
 }
 
+// 1. Removes font-weight bold by inheriting
+// 2. Matches default `<td>` alignment by inheriting `text-align`.
+// 3. Fix alignment for Safari
+
 th {
-  // Matches default `<td>` alignment by inheriting from the `<body>`, or the
-  // closest parent with a set `text-align`.
-  text-align: inherit;
+  font-weight: $table-th-font-weight; // 1
+  text-align: inherit; // 2
+  text-align: -webkit-match-parent; // 3
 }
 
 
@@ -296,17 +303,17 @@ label {
 //
 // Details at https://github.com/twbs/bootstrap/issues/24093
 button {
-  // stylelint-disable-next-line property-blacklist
+  // stylelint-disable-next-line property-disallowed-list
   border-radius: 0;
 }
 
-// Work around a Firefox/IE bug where the transparent `button` background
-// results in a loss of the default `button` focus styles.
-//
-// Credit: https://github.com/suitcss/base/
-button:focus {
-  outline: 1px dotted;
-  outline: 5px auto -webkit-focus-ring-color;
+// Explicitly remove focus outline in Chromium when it shouldn't be
+// visible (e.g. as result of mouse click or touch tap). It already
+// should be doing this automatically, but seems to currently be
+// confused and applies its very visible two-tone outline anyway.
+
+button:focus:not(:focus-visible) {
+  outline: 0;
 }
 
 input,
@@ -330,6 +337,13 @@ select {
   text-transform: none; // Remove the inheritance of text transform in Firefox
 }
 
+// Set the cursor for non-`<button>` buttons
+//
+// Details at https://github.com/twbs/bootstrap/pull/30562
+[role="button"] {
+  cursor: pointer;
+}
+
 // Remove the inheritance of word-wrap in Safari.
 //
 // Details at https://github.com/twbs/bootstrap/issues/24990
@@ -376,18 +390,6 @@ input[type="checkbox"] {
 }
 
 
-input[type="date"],
-input[type="time"],
-input[type="datetime-local"],
-input[type="month"] {
-  // Remove the default appearance of temporal inputs to avoid a Mobile Safari
-  // bug where setting a custom line-height prevents text from being vertically
-  // centered within the input.
-  // See https://bugs.webkit.org/show_bug.cgi?id=139848
-  // and https://github.com/twbs/bootstrap/issues/11266
-  -webkit-appearance: listbox;
-}
-
 textarea {
   overflow: auto; // Remove the default vertical scrollbar in IE.
   // Textareas should really only resize vertically so they don't break their (horizontal) containers.
diff --git a/_sass/bootstrap/_root.scss b/_sass/bootstrap/_root.scss
index 8110030..ad550df 100644
--- a/_sass/bootstrap/_root.scss
+++ b/_sass/bootstrap/_root.scss
@@ -1,4 +1,3 @@
-// Do not forget to update getting-started/theming.md!
 :root {
   // Custom variable values only support SassScript inside `#{}`.
   @each $color, $value in $colors {
diff --git a/_sass/bootstrap/_spinners.scss b/_sass/bootstrap/_spinners.scss
index 364a5c1..7d8fba7 100644
--- a/_sass/bootstrap/_spinners.scss
+++ b/_sass/bootstrap/_spinners.scss
@@ -13,9 +13,9 @@
   vertical-align: text-bottom;
   border: $spinner-border-width solid currentColor;
   border-right-color: transparent;
-  // stylelint-disable-next-line property-blacklist
+  // stylelint-disable-next-line property-disallowed-list
   border-radius: 50%;
-  animation: spinner-border .75s linear infinite;
+  animation: .75s linear infinite spinner-border;
 }
 
 .spinner-border-sm {
@@ -34,6 +34,7 @@
   }
   50% {
     opacity: 1;
+    transform: none;
   }
 }
 
@@ -43,13 +44,22 @@
   height: $spinner-height;
   vertical-align: text-bottom;
   background-color: currentColor;
-  // stylelint-disable-next-line property-blacklist
+  // stylelint-disable-next-line property-disallowed-list
   border-radius: 50%;
   opacity: 0;
-  animation: spinner-grow .75s linear infinite;
+  animation: .75s linear infinite spinner-grow;
 }
 
 .spinner-grow-sm {
   width: $spinner-width-sm;
   height: $spinner-height-sm;
 }
+
+@if $enable-prefers-reduced-motion-media-query {
+  @media (prefers-reduced-motion: reduce) {
+    .spinner-border,
+    .spinner-grow {
+      animation-duration: 1.5s;
+    }
+  }
+}
diff --git a/_sass/bootstrap/_toasts.scss b/_sass/bootstrap/_toasts.scss
index 6aa5352..f9ca8d9 100644
--- a/_sass/bootstrap/_toasts.scss
+++ b/_sass/bootstrap/_toasts.scss
@@ -1,13 +1,14 @@
 .toast {
+  // Prevents from shrinking in IE11, when in a flex container
+  // See https://github.com/twbs/bootstrap/issues/28341
+  flex-basis: $toast-max-width;
   max-width: $toast-max-width;
-  overflow: hidden; // cheap rounded corners on nested items
   @include font-size($toast-font-size);
   color: $toast-color;
   background-color: $toast-background-color;
   background-clip: padding-box;
   border: $toast-border-width solid $toast-border-color;
   box-shadow: $toast-box-shadow;
-  backdrop-filter: blur(10px);
   opacity: 0;
   @include border-radius($toast-border-radius);
 
@@ -37,6 +38,7 @@
   background-color: $toast-header-background-color;
   background-clip: padding-box;
   border-bottom: $toast-border-width solid $toast-header-border-color;
+  @include border-top-radius(subtract($toast-border-radius, $toast-border-width));
 }
 
 .toast-body {
diff --git a/_sass/bootstrap/_type.scss b/_sass/bootstrap/_type.scss
index 43dde7d..3112a73 100644
--- a/_sass/bootstrap/_type.scss
+++ b/_sass/bootstrap/_type.scss
@@ -1,4 +1,4 @@
-// stylelint-disable declaration-no-important, selector-list-comma-newline-after
+// stylelint-disable selector-list-comma-newline-after
 
 //
 // Headings
diff --git a/_sass/bootstrap/_utilities.scss b/_sass/bootstrap/_utilities.scss
index a5de31b..10e31dd 100644
--- a/_sass/bootstrap/_utilities.scss
+++ b/_sass/bootstrap/_utilities.scss
@@ -6,12 +6,13 @@
 @import "utilities/embed";
 @import "utilities/flex";
 @import "utilities/float";
+@import "utilities/interactions";
 @import "utilities/overflow";
 @import "utilities/position";
 @import "utilities/screenreaders";
 @import "utilities/shadows";
 @import "utilities/sizing";
-@import "utilities/stretched-link";
 @import "utilities/spacing";
+@import "utilities/stretched-link";
 @import "utilities/text";
 @import "utilities/visibility";
diff --git a/_sass/bootstrap/_variables.scss b/_sass/bootstrap/_variables.scss
index 5d3135c..0a260b9 100644
--- a/_sass/bootstrap/_variables.scss
+++ b/_sass/bootstrap/_variables.scss
@@ -18,7 +18,6 @@ $gray-900: #212529 !default;
 $black:    #000 !default;
 
 $grays: () !default;
-// stylelint-disable-next-line scss/dollar-variable-default
 $grays: map-merge(
   (
     "100": $gray-100,
@@ -46,7 +45,6 @@ $teal:    #20c997 !default;
 $cyan:    #17a2b8 !default;
 
 $colors: () !default;
-// stylelint-disable-next-line scss/dollar-variable-default
 $colors: map-merge(
   (
     "blue":       $blue,
@@ -76,7 +74,6 @@ $light:         $gray-100 !default;
 $dark:          $gray-800 !default;
 
 $theme-colors: () !default;
-// stylelint-disable-next-line scss/dollar-variable-default
 $theme-colors: map-merge(
   (
     "primary":    $primary,
@@ -103,9 +100,11 @@ $yiq-text-light:            $white !default;
 
 // Characters which are escaped by the escape-svg function
 $escaped-characters: (
-  ("<","%3c"),
-  (">","%3e"),
-  ("#","%23"),
+  ("<", "%3c"),
+  (">", "%3e"),
+  ("#", "%23"),
+  ("(", "%28"),
+  (")", "%29"),
 ) !default;
 
 
@@ -136,7 +135,6 @@ $enable-deprecation-messages:                 true !default;
 
 $spacer: 1rem !default;
 $spacers: () !default;
-// stylelint-disable-next-line scss/dollar-variable-default
 $spacers: map-merge(
   (
     0: 0,
@@ -151,7 +149,6 @@ $spacers: map-merge(
 
 // This variable affects the `.h-*` and `.w-*` classes.
 $sizes: () !default;
-// stylelint-disable-next-line scss/dollar-variable-default
 $sizes: map-merge(
   (
     25: 25%,
@@ -262,7 +259,6 @@ $transition-fade:             opacity .15s linear !default;
 $transition-collapse:         height .35s ease !default;
 
 $embed-responsive-aspect-ratios: () !default;
-// stylelint-disable-next-line scss/dollar-variable-default
 $embed-responsive-aspect-ratios: join(
   (
     (21 9),
@@ -278,7 +274,7 @@ $embed-responsive-aspect-ratios: join(
 // Font, line-height, and color for body text, headings, and more.
 
 // stylelint-disable value-keyword-case
-$font-family-sans-serif:      -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji" !default;
+$font-family-sans-serif:      -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", "Liberation Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji" !default;
 $font-family-monospace:       SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace !default;
 $font-family-base:            $font-family-sans-serif !default;
 // stylelint-enable value-keyword-case
@@ -367,6 +363,7 @@ $table-border-color:          $border-color !default;
 
 $table-head-bg:               $gray-200 !default;
 $table-head-color:            $gray-700 !default;
+$table-th-font-weight:        null !default;
 
 $table-dark-color:            $white !default;
 $table-dark-bg:               $gray-800 !default;
@@ -544,7 +541,7 @@ $custom-control-label-disabled-color:           $gray-600 !default;
 $custom-control-indicator-checked-color:        $component-active-color !default;
 $custom-control-indicator-checked-bg:           $component-active-bg !default;
 $custom-control-indicator-checked-disabled-bg:  rgba(theme-color("primary"), .5) !default;
-$custom-control-indicator-checked-box-shadow:   none !default;
+$custom-control-indicator-checked-box-shadow:   null !default;
 $custom-control-indicator-checked-border-color: $custom-control-indicator-checked-bg !default;
 
 $custom-control-indicator-focus-box-shadow:     $input-focus-box-shadow !default;
@@ -552,7 +549,7 @@ $custom-control-indicator-focus-border-color:   $input-focus-border-color !defau
 
 $custom-control-indicator-active-color:         $component-active-color !default;
 $custom-control-indicator-active-bg:            lighten($component-active-bg, 35%) !default;
-$custom-control-indicator-active-box-shadow:    none !default;
+$custom-control-indicator-active-box-shadow:    null !default;
 $custom-control-indicator-active-border-color:  $custom-control-indicator-active-bg !default;
 
 $custom-checkbox-indicator-border-radius:       $border-radius !default;
@@ -561,7 +558,7 @@ $custom-checkbox-indicator-icon-checked:        url("data:image/svg+xml,<svg xml
 $custom-checkbox-indicator-indeterminate-bg:           $component-active-bg !default;
 $custom-checkbox-indicator-indeterminate-color:        $custom-control-indicator-checked-color !default;
 $custom-checkbox-indicator-icon-indeterminate:         url("data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' width='4' height='4' viewBox='0 0 4 4'><path stroke='#{$custom-checkbox-indicator-indeterminate-color}' d='M0 2h4'/></svg>") !default;
-$custom-checkbox-indicator-indeterminate-box-shadow:   none !default;
+$custom-checkbox-indicator-indeterminate-box-shadow:   null !default;
 $custom-checkbox-indicator-indeterminate-border-color: $custom-checkbox-indicator-indeterminate-bg !default;
 
 $custom-radio-indicator-border-radius:          50% !default;
@@ -586,7 +583,7 @@ $custom-select-disabled-bg:         $gray-200 !default;
 $custom-select-bg-size:             8px 10px !default; // In pixels because image dimensions
 $custom-select-indicator-color:     $gray-800 !default;
 $custom-select-indicator:           url("data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' width='4' height='5' viewBox='0 0 4 5'><path fill='#{$custom-select-indicator-color}' d='M2 0L0 2h4zm0 5L0 3h4z'/></svg>") !default;
-$custom-select-background:          escape-svg($custom-select-indicator) no-repeat right $custom-select-padding-x center / $custom-select-bg-size !default; // Used so we can have multiple background elements (e.g., arrow and feedback icon)
+$custom-select-background:          escape-svg($custom-select-indicator) right $custom-select-padding-x center / $custom-select-bg-size no-repeat !default; // Used so we can have multiple background elements (e.g., arrow and feedback icon)
 
 $custom-select-feedback-icon-padding-right: add(1em * .75, (2 * $custom-select-padding-y * .75) + $custom-select-padding-x + $custom-select-indicator-padding) !default;
 $custom-select-feedback-icon-position:      center right ($custom-select-padding-x + $custom-select-indicator-padding) !default;
@@ -666,7 +663,6 @@ $form-feedback-icon-invalid-color:  $form-feedback-invalid-color !default;
 $form-feedback-icon-invalid:        url("data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' width='12' height='12' fill='none' stroke='#{$form-feedback-icon-invalid-color}' viewBox='0 0 12 12'><circle cx='6' cy='6' r='4.5'/><path stroke-linejoin='round' d='M5.8 3.6h.4L6 6.5z'/><circle cx='6' cy='8.2' r='.6' fill='#{$form-feedback-icon-invalid-color}' stroke='none'/></svg>") !default;
 
 $form-validation-states: () !default;
-// stylelint-disable-next-line scss/dollar-variable-default
 $form-validation-states: map-merge(
   (
     "valid": (
@@ -735,6 +731,8 @@ $navbar-toggler-padding-x:          .75rem !default;
 $navbar-toggler-font-size:          $font-size-lg !default;
 $navbar-toggler-border-radius:      $btn-border-radius !default;
 
+$navbar-nav-scroll-max-height:      75vh !default;
+
 $navbar-dark-color:                 rgba($white, .5) !default;
 $navbar-dark-hover-color:           rgba($white, .75) !default;
 $navbar-dark-active-color:          $white !default;
@@ -760,6 +758,7 @@ $navbar-dark-brand-hover-color:           $navbar-dark-active-color !default;
 // Dropdown menu container and contents.
 
 $dropdown-min-width:                10rem !default;
+$dropdown-padding-x:                0 !default;
 $dropdown-padding-y:                .5rem !default;
 $dropdown-spacer:                   .125rem !default;
 $dropdown-font-size:                $font-size-base !default;
@@ -775,17 +774,18 @@ $dropdown-box-shadow:               0 .5rem 1rem rgba($black, .175) !default;
 
 $dropdown-link-color:               $gray-900 !default;
 $dropdown-link-hover-color:         darken($gray-900, 5%) !default;
-$dropdown-link-hover-bg:            $gray-100 !default;
+$dropdown-link-hover-bg:            $gray-200 !default;
 
 $dropdown-link-active-color:        $component-active-color !default;
 $dropdown-link-active-bg:           $component-active-bg !default;
 
-$dropdown-link-disabled-color:      $gray-600 !default;
+$dropdown-link-disabled-color:      $gray-500 !default;
 
 $dropdown-item-padding-y:           .25rem !default;
 $dropdown-item-padding-x:           1.5rem !default;
 
 $dropdown-header-color:             $gray-600 !default;
+$dropdown-header-padding:           $dropdown-padding-y $dropdown-item-padding-x !default;
 
 
 // Pagination
@@ -818,6 +818,8 @@ $pagination-disabled-color:         $gray-600 !default;
 $pagination-disabled-bg:            $white !default;
 $pagination-disabled-border-color:  $gray-300 !default;
 
+$pagination-border-radius-sm:       $border-radius-sm !default;
+$pagination-border-radius-lg:       $border-radius-lg !default;
 
 // Jumbotron
 
@@ -1135,6 +1137,7 @@ $pre-scrollable-max-height:         340px !default;
 $displays: none, inline, inline-block, block, table, table-row, table-cell, flex, inline-flex !default;
 $overflows: auto, hidden !default;
 $positions: static, relative, absolute, fixed, sticky !default;
+$user-selects: all, auto, none !default;
 
 
 // Printing
diff --git a/_sass/bootstrap/bootstrap-grid.scss b/_sass/bootstrap/bootstrap-grid.scss
index 33e1376..6a66483 100644
--- a/_sass/bootstrap/bootstrap-grid.scss
+++ b/_sass/bootstrap/bootstrap-grid.scss
@@ -1,8 +1,8 @@
 /*!
- * Bootstrap Grid v4.4.1 (https://getbootstrap.com/)
- * Copyright 2011-2019 The Bootstrap Authors
- * Copyright 2011-2019 Twitter, Inc.
- * Licensed under MIT (https://github.com/twbs/bootstrap/blob/master/LICENSE)
+ * Bootstrap Grid v4.6.0 (https://getbootstrap.com/)
+ * Copyright 2011-2021 The Bootstrap Authors
+ * Copyright 2011-2021 Twitter, Inc.
+ * Licensed under MIT (https://github.com/twbs/bootstrap/blob/main/LICENSE)
  */
 
 html {
@@ -19,6 +19,7 @@ html {
 @import "functions";
 @import "variables";
 
+@import "mixins/deprecate";
 @import "mixins/breakpoints";
 @import "mixins/grid-framework";
 @import "mixins/grid";
diff --git a/_sass/bootstrap/bootstrap-reboot.scss b/_sass/bootstrap/bootstrap-reboot.scss
index 5dd6f84..2b6cfc2 100644
--- a/_sass/bootstrap/bootstrap-reboot.scss
+++ b/_sass/bootstrap/bootstrap-reboot.scss
@@ -1,8 +1,8 @@
 /*!
- * Bootstrap Reboot v4.4.1 (https://getbootstrap.com/)
- * Copyright 2011-2019 The Bootstrap Authors
- * Copyright 2011-2019 Twitter, Inc.
- * Licensed under MIT (https://github.com/twbs/bootstrap/blob/master/LICENSE)
+ * Bootstrap Reboot v4.6.0 (https://getbootstrap.com/)
+ * Copyright 2011-2021 The Bootstrap Authors
+ * Copyright 2011-2021 Twitter, Inc.
+ * Licensed under MIT (https://github.com/twbs/bootstrap/blob/main/LICENSE)
  * Forked from Normalize.css, licensed MIT (https://github.com/necolas/normalize.css/blob/master/LICENSE.md)
  */
 
diff --git a/_sass/bootstrap/bootstrap.scss b/_sass/bootstrap/bootstrap.scss
index 881e4d8..e86c49d 100644
--- a/_sass/bootstrap/bootstrap.scss
+++ b/_sass/bootstrap/bootstrap.scss
@@ -1,8 +1,8 @@
 /*!
- * Bootstrap v4.4.1 (https://getbootstrap.com/)
- * Copyright 2011-2019 The Bootstrap Authors
- * Copyright 2011-2019 Twitter, Inc.
- * Licensed under MIT (https://github.com/twbs/bootstrap/blob/master/LICENSE)
+ * Bootstrap v4.6.0 (https://getbootstrap.com/)
+ * Copyright 2011-2021 The Bootstrap Authors
+ * Copyright 2011-2021 Twitter, Inc.
+ * Licensed under MIT (https://github.com/twbs/bootstrap/blob/main/LICENSE)
  */
 
 @import "functions";
diff --git a/_sass/bootstrap/mixins/_background-variant.scss b/_sass/bootstrap/mixins/_background-variant.scss
index 3ceb5c5..8058018 100644
--- a/_sass/bootstrap/mixins/_background-variant.scss
+++ b/_sass/bootstrap/mixins/_background-variant.scss
@@ -15,8 +15,9 @@
   @include deprecate("The `bg-variant` mixin", "v4.4.0", "v5", $ignore-warning);
 }
 
-@mixin bg-gradient-variant($parent, $color) {
+@mixin bg-gradient-variant($parent, $color, $ignore-warning: false) {
   #{$parent} {
     background: $color linear-gradient(180deg, mix($body-bg, $color, 15%), $color) repeat-x !important;
   }
+  @include deprecate("The `bg-gradient-variant` mixin", "v4.5.0", "v5", $ignore-warning);
 }
diff --git a/_sass/bootstrap/mixins/_border-radius.scss b/_sass/bootstrap/mixins/_border-radius.scss
index 88aeb37..4fad91d 100644
--- a/_sass/bootstrap/mixins/_border-radius.scss
+++ b/_sass/bootstrap/mixins/_border-radius.scss
@@ -1,9 +1,22 @@
-// stylelint-disable property-blacklist
+// stylelint-disable property-disallowed-list
 // Single side border-radius
 
+// Helper function to replace negative values with 0
+@function valid-radius($radius) {
+  $return: ();
+  @each $value in $radius {
+    @if type-of($value) == number {
+      $return: append($return, max($value, 0));
+    } @else {
+      $return: append($return, $value);
+    }
+  }
+  @return $return;
+}
+
 @mixin border-radius($radius: $border-radius, $fallback-border-radius: false) {
   @if $enable-rounded {
-    border-radius: $radius;
+    border-radius: valid-radius($radius);
   }
   @else if $fallback-border-radius != false {
     border-radius: $fallback-border-radius;
@@ -12,52 +25,52 @@
 
 @mixin border-top-radius($radius) {
   @if $enable-rounded {
-    border-top-left-radius: $radius;
-    border-top-right-radius: $radius;
+    border-top-left-radius: valid-radius($radius);
+    border-top-right-radius: valid-radius($radius);
   }
 }
 
 @mixin border-right-radius($radius) {
   @if $enable-rounded {
-    border-top-right-radius: $radius;
-    border-bottom-right-radius: $radius;
+    border-top-right-radius: valid-radius($radius);
+    border-bottom-right-radius: valid-radius($radius);
   }
 }
 
 @mixin border-bottom-radius($radius) {
   @if $enable-rounded {
-    border-bottom-right-radius: $radius;
-    border-bottom-left-radius: $radius;
+    border-bottom-right-radius: valid-radius($radius);
+    border-bottom-left-radius: valid-radius($radius);
   }
 }
 
 @mixin border-left-radius($radius) {
   @if $enable-rounded {
-    border-top-left-radius: $radius;
-    border-bottom-left-radius: $radius;
+    border-top-left-radius: valid-radius($radius);
+    border-bottom-left-radius: valid-radius($radius);
   }
 }
 
 @mixin border-top-left-radius($radius) {
   @if $enable-rounded {
-    border-top-left-radius: $radius;
+    border-top-left-radius: valid-radius($radius);
   }
 }
 
 @mixin border-top-right-radius($radius) {
   @if $enable-rounded {
-    border-top-right-radius: $radius;
+    border-top-right-radius: valid-radius($radius);
   }
 }
 
 @mixin border-bottom-right-radius($radius) {
   @if $enable-rounded {
-    border-bottom-right-radius: $radius;
+    border-bottom-right-radius: valid-radius($radius);
   }
 }
 
 @mixin border-bottom-left-radius($radius) {
   @if $enable-rounded {
-    border-bottom-left-radius: $radius;
+    border-bottom-left-radius: valid-radius($radius);
   }
 }
diff --git a/_sass/bootstrap/mixins/_buttons.scss b/_sass/bootstrap/mixins/_buttons.scss
index c82c4d6..d6235aa 100644
--- a/_sass/bootstrap/mixins/_buttons.scss
+++ b/_sass/bootstrap/mixins/_buttons.scss
@@ -20,10 +20,10 @@
     color: color-yiq($hover-background);
     @include gradient-bg($hover-background);
     border-color: $hover-border;
-    // Avoid using mixin so we can pass custom focus shadow properly
     @if $enable-shadows {
-      box-shadow: $btn-box-shadow, 0 0 0 $btn-focus-width rgba(mix(color-yiq($background), $border, 15%), .5);
+      @include box-shadow($btn-box-shadow, 0 0 0 $btn-focus-width rgba(mix(color-yiq($background), $border, 15%), .5));
     } @else {
+      // Avoid using mixin so we can pass custom focus shadow properly
       box-shadow: 0 0 0 $btn-focus-width rgba(mix(color-yiq($background), $border, 15%), .5);
     }
   }
@@ -51,10 +51,10 @@
     border-color: $active-border;
 
     &:focus {
-      // Avoid using mixin so we can pass custom focus shadow properly
       @if $enable-shadows and $btn-active-box-shadow != none {
-        box-shadow: $btn-active-box-shadow, 0 0 0 $btn-focus-width rgba(mix(color-yiq($background), $border, 15%), .5);
+        @include box-shadow($btn-active-box-shadow, 0 0 0 $btn-focus-width rgba(mix(color-yiq($background), $border, 15%), .5));
       } @else {
+        // Avoid using mixin so we can pass custom focus shadow properly
         box-shadow: 0 0 0 $btn-focus-width rgba(mix(color-yiq($background), $border, 15%), .5);
       }
     }
@@ -90,10 +90,10 @@
     border-color: $active-border;
 
     &:focus {
-      // Avoid using mixin so we can pass custom focus shadow properly
       @if $enable-shadows and $btn-active-box-shadow != none {
-        box-shadow: $btn-active-box-shadow, 0 0 0 $btn-focus-width rgba($color, .5);
+        @include box-shadow($btn-active-box-shadow, 0 0 0 $btn-focus-width rgba($color, .5));
       } @else {
+        // Avoid using mixin so we can pass custom focus shadow properly
         box-shadow: 0 0 0 $btn-focus-width rgba($color, .5);
       }
     }
diff --git a/_sass/bootstrap/mixins/_forms.scss b/_sass/bootstrap/mixins/_forms.scss
index 418470d..a321630 100644
--- a/_sass/bootstrap/mixins/_forms.scss
+++ b/_sass/bootstrap/mixins/_forms.scss
@@ -16,10 +16,10 @@
     background-color: $input-focus-bg;
     border-color: $input-focus-border-color;
     outline: 0;
-    // Avoid using mixin so we can pass custom focus shadow properly
     @if $enable-shadows {
-      box-shadow: $input-box-shadow, $input-focus-box-shadow;
+      @include box-shadow($input-box-shadow, $input-focus-box-shadow);
     } @else {
+      // Avoid using mixin so we can pass custom focus shadow properly
       box-shadow: $input-focus-box-shadow;
     }
   }
@@ -53,6 +53,7 @@
   .#{$state}-tooltip {
     position: absolute;
     top: 100%;
+    left: 0;
     z-index: 5;
     display: none;
     max-width: 100%; // Contain to parent when possible
@@ -63,6 +64,13 @@
     color: color-yiq($color);
     background-color: rgba($color, $form-feedback-tooltip-opacity);
     @include border-radius($form-feedback-tooltip-border-radius);
+
+    // See https://github.com/twbs/bootstrap/pull/31557
+    // Align tooltip to form elements
+    .form-row > .col > &,
+    .form-row > [class*="col-"] > & {
+      left: $form-grid-gutter-width / 2;
+    }
   }
 
   @include form-validation-state-selector($state) {
@@ -107,7 +115,7 @@
 
       @if $enable-validation-icons {
         padding-right: $custom-select-feedback-icon-padding-right;
-        background: $custom-select-background, escape-svg($icon) $custom-select-bg no-repeat $custom-select-feedback-icon-position / $custom-select-feedback-icon-size;
+        background: $custom-select-background, $custom-select-bg escape-svg($icon) $custom-select-feedback-icon-position / $custom-select-feedback-icon-size no-repeat;
       }
 
       &:focus {
diff --git a/_sass/bootstrap/mixins/_grid-framework.scss b/_sass/bootstrap/mixins/_grid-framework.scss
index 8e291f7..6fc8e85 100644
--- a/_sass/bootstrap/mixins/_grid-framework.scss
+++ b/_sass/bootstrap/mixins/_grid-framework.scss
@@ -15,12 +15,15 @@
   @each $breakpoint in map-keys($breakpoints) {
     $infix: breakpoint-infix($breakpoint, $breakpoints);
 
-    // Allow columns to stretch full width below their breakpoints
-    @for $i from 1 through $columns {
-      .col#{$infix}-#{$i} {
-        @extend %grid-column;
+    @if $columns > 0 {
+      // Allow columns to stretch full width below their breakpoints
+      @for $i from 1 through $columns {
+        .col#{$infix}-#{$i} {
+          @extend %grid-column;
+        }
       }
     }
+
     .col#{$infix},
     .col#{$infix}-auto {
       @extend %grid-column;
@@ -34,9 +37,11 @@
         max-width: 100%;
       }
 
-      @for $i from 1 through $grid-row-columns {
-        .row-cols#{$infix}-#{$i} {
-          @include row-cols($i);
+      @if $grid-row-columns > 0 {
+        @for $i from 1 through $grid-row-columns {
+          .row-cols#{$infix}-#{$i} {
+            @include row-cols($i);
+          }
         }
       }
 
@@ -44,9 +49,11 @@
         @include make-col-auto();
       }
 
-      @for $i from 1 through $columns {
-        .col#{$infix}-#{$i} {
-          @include make-col($i, $columns);
+      @if $columns > 0 {
+        @for $i from 1 through $columns {
+          .col#{$infix}-#{$i} {
+            @include make-col($i, $columns);
+          }
         }
       }
 
@@ -58,11 +65,13 @@
         .order#{$infix}-#{$i} { order: $i; }
       }
 
-      // `$columns - 1` because offsetting by the width of an entire row isn't possible
-      @for $i from 0 through ($columns - 1) {
-        @if not ($infix == "" and $i == 0) { // Avoid emitting useless .offset-0
-          .offset#{$infix}-#{$i} {
-            @include make-col-offset($i, $columns);
+      @if $columns > 0 {
+        // `$columns - 1` because offsetting by the width of an entire row isn't possible
+        @for $i from 0 through ($columns - 1) {
+          @if not ($infix == "" and $i == 0) { // Avoid emitting useless .offset-0
+            .offset#{$infix}-#{$i} {
+              @include make-col-offset($i, $columns);
+            }
           }
         }
       }
diff --git a/_sass/bootstrap/mixins/_grid.scss b/_sass/bootstrap/mixins/_grid.scss
index b1240b0..19babc0 100644
--- a/_sass/bootstrap/mixins/_grid.scss
+++ b/_sass/bootstrap/mixins/_grid.scss
@@ -10,6 +10,12 @@
   margin-left: auto;
 }
 
+@mixin make-row($gutter: $grid-gutter-width) {
+  display: flex;
+  flex-wrap: wrap;
+  margin-right: -$gutter / 2;
+  margin-left: -$gutter / 2;
+}
 
 // For each breakpoint, define the maximum width of the container in a media query
 @mixin make-container-max-widths($max-widths: $container-max-widths, $breakpoints: $grid-breakpoints) {
@@ -18,13 +24,7 @@
       max-width: $container-max-width;
     }
   }
-}
-
-@mixin make-row($gutter: $grid-gutter-width) {
-  display: flex;
-  flex-wrap: wrap;
-  margin-right: -$gutter / 2;
-  margin-left: -$gutter / 2;
+  @include deprecate("The `make-container-max-widths` mixin", "v4.5.2", "v5");
 }
 
 @mixin make-col-ready($gutter: $grid-gutter-width) {
@@ -62,7 +62,7 @@
 // numberof columns. Supports wrapping to new lines, but does not do a Masonry
 // style grid.
 @mixin row-cols($count) {
-  & > * {
+  > * {
     flex: 0 0 100% / $count;
     max-width: 100% / $count;
   }
diff --git a/_sass/bootstrap/mixins/_image.scss b/_sass/bootstrap/mixins/_image.scss
index c971e03..3aaa0d7 100644
--- a/_sass/bootstrap/mixins/_image.scss
+++ b/_sass/bootstrap/mixins/_image.scss
@@ -26,7 +26,7 @@
   // Autoprefixer takes care of adding -webkit-min-device-pixel-ratio and -o-min-device-pixel-ratio,
   // but doesn't convert dppx=>dpi.
   // There's no such thing as unprefixed min-device-pixel-ratio since it's nonstandard.
-  // Compatibility info: https://caniuse.com/#feat=css-media-resolution
+  // Compatibility info: https://caniuse.com/css-media-resolution
   @media only screen and (min-resolution: 192dpi), // IE9-11 don't support dppx
     only screen and (min-resolution: 2dppx) { // Standardized
     background-image: url($file-2x);
diff --git a/_sass/bootstrap/mixins/_screen-reader.scss b/_sass/bootstrap/mixins/_screen-reader.scss
index 2123039..6913442 100644
--- a/_sass/bootstrap/mixins/_screen-reader.scss
+++ b/_sass/bootstrap/mixins/_screen-reader.scss
@@ -1,6 +1,6 @@
 // Only display content to screen readers
 //
-// See: https://a11yproject.com/posts/how-to-hide-content/
+// See: https://www.a11yproject.com/posts/2013-01-11-how-to-hide-content/
 // See: https://hugogiraudel.com/2016/10/13/css-hide-and-seek/
 
 @mixin sr-only() {
diff --git a/_sass/bootstrap/mixins/_transition.scss b/_sass/bootstrap/mixins/_transition.scss
index 8ce35a6..54870bf 100644
--- a/_sass/bootstrap/mixins/_transition.scss
+++ b/_sass/bootstrap/mixins/_transition.scss
@@ -1,16 +1,26 @@
-// stylelint-disable property-blacklist
+// stylelint-disable property-disallowed-list
 @mixin transition($transition...) {
-  @if $enable-transitions {
-    @if length($transition) == 0 {
-      transition: $transition-base;
-    } @else {
-      transition: $transition;
+  @if length($transition) == 0 {
+    $transition: $transition-base;
+  }
+
+  @if length($transition) > 1 {
+    @each $value in $transition {
+      @if $value == null or $value == none {
+        @warn "The keyword 'none' or 'null' must be used as a single argument.";
+      }
     }
   }
 
-  @if $enable-prefers-reduced-motion-media-query {
-    @media (prefers-reduced-motion: reduce) {
-      transition: none;
+  @if $enable-transitions {
+    @if nth($transition, 1) != null {
+      transition: $transition;
+    }
+
+    @if $enable-prefers-reduced-motion-media-query and nth($transition, 1) != null and nth($transition, 1) != none {
+      @media (prefers-reduced-motion: reduce) {
+        transition: none;
+      }
     }
   }
 }
diff --git a/_sass/bootstrap/utilities/_background.scss b/_sass/bootstrap/utilities/_background.scss
index a997b1b..3accbc4 100644
--- a/_sass/bootstrap/utilities/_background.scss
+++ b/_sass/bootstrap/utilities/_background.scss
@@ -6,7 +6,7 @@
 
 @if $enable-gradients {
   @each $color, $value in $theme-colors {
-    @include bg-gradient-variant(".bg-gradient-#{$color}", $value);
+    @include bg-gradient-variant(".bg-gradient-#{$color}", $value, true);
   }
 }
 
diff --git a/_sass/bootstrap/utilities/_borders.scss b/_sass/bootstrap/utilities/_borders.scss
index 302f6bf..205f3fc 100644
--- a/_sass/bootstrap/utilities/_borders.scss
+++ b/_sass/bootstrap/utilities/_borders.scss
@@ -1,4 +1,4 @@
-// stylelint-disable property-blacklist, declaration-no-important
+// stylelint-disable property-disallowed-list, declaration-no-important
 
 //
 // Border
diff --git a/_sass/bootstrap/utilities/_interactions.scss b/_sass/bootstrap/utilities/_interactions.scss
new file mode 100644
index 0000000..cc75fc2
--- /dev/null
+++ b/_sass/bootstrap/utilities/_interactions.scss
@@ -0,0 +1,5 @@
+// stylelint-disable declaration-no-important
+
+@each $value in $user-selects {
+  .user-select-#{$value} { user-select: $value !important; }
+}
diff --git a/_sass/bootstrap/utilities/_text.scss b/_sass/bootstrap/utilities/_text.scss
index 5d0f1c8..3a9f83e 100644
--- a/_sass/bootstrap/utilities/_text.scss
+++ b/_sass/bootstrap/utilities/_text.scss
@@ -63,8 +63,8 @@
 .text-decoration-none { text-decoration: none !important; }
 
 .text-break {
-  word-break: break-word !important; // IE & < Edge 18
-  overflow-wrap: break-word !important;
+  word-break: break-word !important; // Deprecated, but avoids issues with flex containers
+  word-wrap: break-word !important; // Used instead of `overflow-wrap` for IE & Edge Legacy
 }
 
 // Reset
diff --git a/assets/css/style.scss b/assets/css/style.scss
index fe5739c..f88f39a 100644
--- a/assets/css/style.scss
+++ b/assets/css/style.scss
@@ -1,5 +1,4 @@
 ---
-# this ensures Jekyll reads the file to be transformed into CSS later
 ---
 
 // Colors