Bootstrap 5 Animated Snow Login Form

<section class="wdw-stage wdw-aurora wdw-snow-stage position-relative overflow-hidden">
  <canvas id="snowCanvas" class="wdw-snow" aria-hidden="true"></canvas>
  <div class="container position-relative" style="max-width:420px">
    <div class="wdw-glass p-4 p-md-5" data-bs-theme="dark">
      <div class="text-center mb-4">
        <span class="wdw-icon mx-auto mb-3" style="width:3.25rem;height:3.25rem"><svg width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.75" stroke-linecap="round" stroke-linejoin="round"><path d="M12 2v20M4.9 7l14.2 10M4.9 17L19.1 7M9 3.5l3 2.5 3-2.5M9 20.5l3-2.5 3 2.5"/></svg></span>
        <h2 class="wdw-heading h3 mb-1">Welcome back</h2>
        <p class="wdw-muted mb-0">Sign in to your account</p>
      </div>
      <form novalidate id="snowForm">
        <div class="form-floating mb-3"><input type="text" class="form-control" id="snUser" placeholder="Username" autocomplete="username"><label for="snUser">Username</label></div>
        <div class="form-floating mb-3"><input type="password" class="form-control" id="snPass" placeholder="Password" autocomplete="current-password"><label for="snPass">Password</label></div>
        <div class="d-flex justify-content-between align-items-center mb-4">
          <div class="form-check mb-0 d-flex align-items-center gap-2 ps-0"><input class="form-check-input m-0" type="checkbox" id="snRem"><label class="form-check-label small" for="snRem">Remember me</label></div>
          <a href="#" class="small link-light link-underline-opacity-0 link-underline-opacity-100-hover">Forgot password?</a>
        </div>
        <button class="btn btn-primary rounded-pill w-100" type="submit">Log in</button>
      </form>
    </div>
  </div>
</section>

/* Web Designer Wall library style — shared base for every Bootstrap 5 snippet.
   Indigo accent, Plus Jakarta Sans, soft cards, pill buttons. Works in light and dark. */
@import url("https://fonts.googleapis.com/css2?family=Plus+Jakarta+Sans:wght@400;500;600;700;800&display=swap");

:root,
[data-bs-theme="light"] {
  --wdw-font: "Plus Jakarta Sans", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --bs-body-font-family: var(--wdw-font);
  --bs-primary: #4f46e5;
  --bs-primary-rgb: 79, 70, 229;
  --bs-primary-text-emphasis: #3730a3;
  --bs-primary-bg-subtle: #eef2ff;
  --bs-primary-border-subtle: #c7d2fe;
  --bs-link-color: #4f46e5;
  --bs-link-color-rgb: 79, 70, 229;
  --bs-link-hover-color: #4338ca;
  --bs-link-hover-color-rgb: 67, 56, 202;
  --bs-focus-ring-color: rgba(79, 70, 229, 0.25);
  --bs-border-radius: 0.75rem;
  --bs-border-radius-lg: 1rem;
  --bs-border-radius-xl: 1.25rem;
  --wdw-radius-card: 1.25rem;
  --wdw-shadow: 0 1px 2px rgba(16, 24, 40, 0.05), 0 16px 40px -16px rgba(16, 24, 40, 0.22);
  --wdw-shadow-sm: 0 1px 2px rgba(16, 24, 40, 0.06), 0 4px 12px -4px rgba(16, 24, 40, 0.12);
  --wdw-stage: #f5f6fb;
}

[data-bs-theme="dark"] {
  --bs-primary: #818cf8;
  --bs-primary-rgb: 129, 140, 248;
  --bs-primary-text-emphasis: #c7d2fe;
  --bs-primary-bg-subtle: rgba(129, 140, 248, 0.14);
  --bs-primary-border-subtle: rgba(129, 140, 248, 0.35);
  --bs-link-color: #a5b4fc;
  --bs-link-color-rgb: 165, 180, 252;
  --bs-link-hover-color: #c7d2fe;
  --bs-link-hover-color-rgb: 199, 210, 254;
  --bs-focus-ring-color: rgba(129, 140, 248, 0.35);
  --wdw-shadow: 0 1px 2px rgba(0, 0, 0, 0.4), 0 16px 40px -16px rgba(0, 0, 0, 0.7);
  --wdw-shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.4), 0 4px 12px -4px rgba(0, 0, 0, 0.5);
  --wdw-stage: #0f1117;
}

body { font-family: var(--wdw-font); -webkit-font-smoothing: antialiased; }

/* Bootstrap compiles its blue into these components; point them at the accent. */
.btn-primary {
  --bs-btn-bg: var(--bs-primary); --bs-btn-border-color: var(--bs-primary);
  --bs-btn-hover-bg: #4338ca; --bs-btn-hover-border-color: #4338ca;
  --bs-btn-active-bg: #3730a3; --bs-btn-active-border-color: #3730a3;
  --bs-btn-disabled-bg: var(--bs-primary); --bs-btn-disabled-border-color: var(--bs-primary);
  --bs-btn-focus-shadow-rgb: var(--bs-primary-rgb);
}
[data-bs-theme="dark"] .btn-primary { --bs-btn-color: #0f1117; --bs-btn-hover-bg: #a5b4fc; --bs-btn-hover-border-color: #a5b4fc; --bs-btn-hover-color: #0f1117; --bs-btn-active-color: #0f1117; }
.btn-outline-primary {
  --bs-btn-color: var(--bs-primary); --bs-btn-border-color: var(--bs-primary);
  --bs-btn-hover-bg: var(--bs-primary); --bs-btn-hover-border-color: var(--bs-primary);
  --bs-btn-active-bg: var(--bs-primary); --bs-btn-active-border-color: var(--bs-primary);
  --bs-btn-focus-shadow-rgb: var(--bs-primary-rgb);
}
.btn { --bs-btn-font-weight: 600; min-height: 44px; display: inline-flex; align-items: center; justify-content: center; gap: .5rem; }
.btn-sm { min-height: 36px; }
.form-control, .form-select { min-height: 44px; border-radius: .75rem; }
.form-control:focus, .form-select:focus, .form-check-input:focus { border-color: rgba(var(--bs-primary-rgb), .6); box-shadow: 0 0 0 .25rem var(--bs-focus-ring-color); }
.form-check-input:checked { background-color: var(--bs-primary); border-color: var(--bs-primary); }
.nav-pills { --bs-nav-pills-link-active-bg: var(--bs-primary); }
.nav { --bs-nav-link-color: var(--bs-secondary-color); --bs-nav-link-hover-color: var(--bs-emphasis-color); }
.pagination { --bs-pagination-active-bg: var(--bs-primary); --bs-pagination-active-border-color: var(--bs-primary); --bs-pagination-color: var(--bs-body-color); --bs-pagination-focus-box-shadow: 0 0 0 .25rem var(--bs-focus-ring-color); }
.progress, .progress-stacked { --bs-progress-bar-bg: var(--bs-primary); }
.list-group { --bs-list-group-active-bg: var(--bs-primary); --bs-list-group-active-border-color: var(--bs-primary); }
.dropdown-menu { --bs-dropdown-link-active-bg: var(--bs-primary); border-radius: .875rem; box-shadow: var(--wdw-shadow-sm); }
.accordion { --bs-accordion-active-bg: var(--bs-primary-bg-subtle); --bs-accordion-active-color: var(--bs-primary-text-emphasis); --bs-accordion-btn-focus-box-shadow: 0 0 0 .25rem var(--bs-focus-ring-color); }
.badge { font-weight: 600; }

/* Library building blocks — use these instead of re-inventing them per snippet. */
.wdw-stage { min-height: 100vh; display: flex; align-items: center; background: var(--wdw-stage); padding-block: 3rem; }
.wdw-card { background: var(--bs-body-bg); border: 1px solid var(--bs-border-color-translucent); border-radius: var(--wdw-radius-card); box-shadow: var(--wdw-shadow); }
.wdw-card-sm { background: var(--bs-body-bg); border: 1px solid var(--bs-border-color-translucent); border-radius: 1rem; box-shadow: var(--wdw-shadow-sm); }
.wdw-aurora { position: relative; color: #fff; background: radial-gradient(60% 55% at 100% 0, #818cf8 0, transparent 70%), radial-gradient(65% 60% at 0 100%, #ec4899 0, transparent 65%), #1e1b4b; }
.wdw-eyebrow { display: inline-block; font-size: .75rem; font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--bs-primary); }
.wdw-heading { font-weight: 800; letter-spacing: -.02em; color: var(--bs-emphasis-color); }
.wdw-muted { color: var(--bs-secondary-color); }
.wdw-icon { width: 2.75rem; height: 2.75rem; flex: none; display: inline-flex; align-items: center; justify-content: center; border-radius: .875rem; background: var(--bs-primary-bg-subtle); color: var(--bs-primary); }

/* Component */
.wdw-snow { position: absolute; inset: 0; width: 100%; height: 100%; pointer-events: none; }
.wdw-glass { background: rgba(255,255,255,.14); backdrop-filter: blur(18px) saturate(1.2); -webkit-backdrop-filter: blur(18px) saturate(1.2); border: 1px solid rgba(255,255,255,.4); border-radius: 1.5rem; box-shadow: 0 30px 60px -20px rgba(0,0,0,.55); color: #fff; }
.wdw-glass .form-control { background: rgba(255,255,255,.1); border-color: rgba(255,255,255,.35); color: #fff; }
.wdw-glass .form-control:focus { background: rgba(255,255,255,.16); }
.wdw-glass .form-floating > label { color: rgba(255,255,255,.8); }
.wdw-glass .form-check-input:not(:checked) { background-color: rgba(255,255,255,.12); border-color: rgba(255,255,255,.55); }

(function () {
  function initSnow() {
    var c = document.getElementById('snowCanvas');
    if (!c) return;
    var ctx = c.getContext('2d'), flakes = [], w = 0, h = 0, raf = 0, visible = true;
    var still = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
    function make() {
      var depth = Math.random();
      var big = depth > .93;
      return { x: Math.random() * w, y: Math.random() * h, p: Math.random() * 6,
        r: big ? Math.random() * 10 + 8 : Math.random() * 2.6 + .6,
        v: big ? Math.random() * .6 + .9 : Math.random() * .8 + .25 + depth * .4,
        a: big ? .14 + Math.random() * .1 : .3 + depth * .6, big: big };
    }
    function size() {
      var r = c.parentElement.getBoundingClientRect();
      w = c.width = r.width; h = c.height = r.height;
      var n = Math.min(w < 576 ? 45 : 140, Math.round(w * h / 9000));
      while (flakes.length < n) flakes.push(make());
      flakes.length = n;
    }
    function draw() {
      raf = 0;
      ctx.clearRect(0, 0, w, h);
      flakes.forEach(function (f) {
        if (f.big) {
          var g = ctx.createRadialGradient(f.x, f.y, 0, f.x, f.y, f.r);
          g.addColorStop(0, 'rgba(255,255,255,' + f.a + ')'); g.addColorStop(1, 'rgba(255,255,255,0)');
          ctx.fillStyle = g;
          ctx.beginPath(); ctx.arc(f.x, f.y, f.r, 0, 6.283); ctx.fill();
        } else {
          ctx.fillStyle = 'rgba(255,255,255,' + f.a + ')';
          ctx.beginPath(); ctx.arc(f.x, f.y, f.r, 0, 6.283); ctx.fill();
        }
        if (still) return;
        f.y += f.v; f.p += .012 + f.v * .006; f.x += Math.sin(f.p) * (.2 + f.v * .3);
        if (f.y > h + f.r) { f.y = -f.r; f.x = Math.random() * w; }
      });
      if (!still && visible && !document.hidden) raf = requestAnimationFrame(draw);
    }
    function kick() { if (!raf) raf = requestAnimationFrame(draw); }
    size(); draw();
    window.addEventListener('resize', function () { size(); if (still) draw(); });
    if (!still) {
      document.addEventListener('visibilitychange', kick);
      if ('IntersectionObserver' in window) new IntersectionObserver(function (e) { visible = e[0].isIntersecting; if (visible) kick(); }).observe(c.parentElement);
    }
    var f = document.getElementById('snowForm');
    if (f) f.addEventListener('submit', function (e) { e.preventDefault(); });
  }
  initSnow();
})();