:root {
  color-scheme: light;
  --ink: #172033;
  --muted: #5c667a;
  --line: #d9e1ec;
  --paper: #f7f9fc;
  --panel: #ffffff;
  --blue: #1463ff;
  --teal: #00897b;
  --yellow: #f3c542;
  --red: #e45545;
  --green: #4b9f47;
  --topbar: #0b4f5f;
  --topbar-deep: #07313b;
  --card-border: #7893b5;
  --shadow: 0 18px 38px rgba(23, 32, 51, 0.12);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  background: var(--paper);
  color: var(--ink);
  font-family: Arial, Helvetica, sans-serif;
  line-height: 1.5;
}

a {
  color: inherit;
}

.top-shell {
  position: sticky;
  top: 0;
  z-index: 10;
  background: linear-gradient(90deg, var(--topbar-deep), var(--topbar));
  border-bottom: 3px solid #f3c542;
  backdrop-filter: blur(10px);
  box-shadow: 0 12px 30px rgba(23, 32, 51, 0.22);
}

.site-header {
  display: flex;
  align-items: center;
  justify-content: flex-start;
  gap: 18px;
  flex-wrap: wrap;
  padding: 12px clamp(12px, 2vw, 28px) 8px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
}

.brand-logo {
  width: 94px;
  height: 62px;
  object-fit: contain;
  display: block;
  background: #ffffff;
  border: 2px solid rgba(255, 255, 255, 0.78);
  border-radius: 14px;
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.22);
  padding: 4px;
}

.site-title {
  min-width: 0;
  flex: 1 1 420px;
}

main {
  width: calc(100% - 24px);
  margin: 0 auto;
}

.hero {
  padding: 12px 0 18px;
}

.eyebrow {
  margin: 0 0 12px;
  color: var(--teal);
  font-size: 15px;
  font-weight: 800;
}

h1 {
  margin: 0;
  max-width: none;
  font-size: clamp(22px, 2.3vw, 42px);
  line-height: 1.1;
  letter-spacing: 0;
  color: #ffffff;
}

.intro {
  max-width: none;
  margin: 0;
  color: var(--muted);
  font-size: 17px;
  font-weight: 600;
}

.header-actions {
  display: flex;
  flex: 0 1 auto;
  flex-wrap: wrap;
  gap: 10px;
  justify-content: flex-end;
  margin-left: auto;
}

.toolbar {
  display: grid;
  grid-template-columns: 1fr;
  gap: 10px;
  align-items: start;
  padding: 8px clamp(12px, 2vw, 28px) 12px;
}

.icon-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  min-height: 42px;
  border: 2px solid rgba(255, 255, 255, 0.72);
  border-radius: 8px;
  background: #f7fbff;
  color: #07313b;
  cursor: pointer;
  font-size: 15px;
  font-weight: 800;
  padding: 0 12px;
  box-shadow: 0 6px 16px rgba(23, 32, 51, 0.08);
}

.toolbar-link {
  text-decoration: none;
}

.icon-button:hover,
.icon-button:focus-visible,
.icon-button[aria-expanded="true"] {
  background: #fff7d6;
  border-color: var(--yellow);
  color: #07313b;
  outline: none;
}

.icon-button svg {
  width: 20px;
  height: 20px;
  fill: none;
  stroke: currentColor;
  stroke-linecap: round;
  stroke-linejoin: round;
  stroke-width: 2.4;
}

.help-button {
  width: 42px;
  padding: 0;
  font-size: 22px;
}

.language-toggle {
  flex-direction: column;
  gap: 2px;
  min-width: 112px;
  padding: 5px 12px;
}

.language-flags {
  display: flex;
  gap: 6px;
  justify-content: center;
  line-height: 1;
}

.language-flags img {
  display: block;
  width: 28px;
  height: 18px;
  border: 1px solid rgba(7, 49, 59, 0.25);
  border-radius: 2px;
  object-fit: cover;
}

.search-panel,
.help-panel {
  grid-column: 1 / -1;
  background: var(--panel);
  border: 2px solid #d8e2ef;
  border-radius: 8px;
  box-shadow: 0 8px 18px rgba(23, 32, 51, 0.1);
  padding: 12px;
}

.help-panel h2 {
  margin: 0 0 8px;
  font-size: 20px;
}

.help-panel ul {
  margin: 0;
  padding-left: 20px;
  color: var(--muted);
  font-weight: 700;
}

.help-panel li + li {
  margin-top: 4px;
}

.search-label {
  display: block;
  margin-bottom: 8px;
  font-size: 14px;
  color: var(--muted);
  font-weight: 800;
}

#search-input {
  width: 100%;
  min-height: 48px;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 0 14px;
  color: var(--ink);
  font-size: 17px;
}

#search-input:focus {
  outline: 3px solid rgba(20, 99, 255, 0.2);
  border-color: var(--blue);
}

.filter-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(156px, 1fr));
  gap: 10px;
  margin-top: 0;
  grid-column: 1;
  grid-row: 1;
}

.filter-button {
  min-height: 38px;
  border: 2px solid rgba(255, 255, 255, 0.7);
  border-radius: 8px;
  background: #fff;
  color: var(--ink);
  padding: 0 14px;
  cursor: pointer;
  font-weight: 800;
  width: 100%;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  line-height: 1.15;
}

.filter-button:hover,
.filter-button:focus-visible,
.filter-button.is-active {
  background: var(--blue);
  border-color: var(--blue);
  color: #fff;
}

.results-heading {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 16px;
  padding: 34px 0 16px;
}

.results-heading h2 {
  margin: 0;
  font-size: 30px;
}

.results-heading p {
  margin: 0;
  color: var(--muted);
  font-weight: 700;
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 14px;
  padding-bottom: 54px;
}

.resource-card {
  min-width: 0;
  background: var(--panel);
  border: 2px solid var(--card-border);
  border-radius: 8px;
  overflow: hidden;
  box-shadow: 0 12px 26px rgba(23, 32, 51, 0.16);
  transition: transform 160ms ease, box-shadow 160ms ease, border-color 160ms ease;
}

.resource-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow);
  border-color: rgba(20, 99, 255, 0.42);
}

.card-link {
  display: grid;
  grid-template-rows: 168px 1fr;
  height: 100%;
  text-decoration: none;
}

.thumb {
  position: relative;
  overflow: hidden;
  background: #ffffff;
}

.thumb img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  object-position: center center;
  display: block;
}

.thumb img:not([src]) {
  display: none;
}

.generated-thumb {
  display: none;
  width: 100%;
  height: 100%;
}

.thumb img:not([src]) + .generated-thumb {
  display: block;
}

.generated-thumb::before,
.generated-thumb::after {
  content: "";
  position: absolute;
}

.thumb[data-visual="heat"] .generated-thumb {
  background: radial-gradient(circle at 72% 68%, #e45545 0 7px, transparent 8px),
    radial-gradient(circle at 63% 54%, #e45545 0 6px, transparent 7px),
    radial-gradient(circle at 78% 45%, #e45545 0 5px, transparent 6px),
    radial-gradient(circle at 36% 42%, #1463ff 0 6px, transparent 7px),
    radial-gradient(circle at 24% 61%, #1463ff 0 5px, transparent 6px),
    #ffffff;
}

.thumb[data-visual="waves"] .generated-thumb {
  background: repeating-radial-gradient(ellipse at center, transparent 0 20px, #1463ff 21px 24px, transparent 25px 44px), #ffffff;
}

.thumb[data-visual="motion"] .generated-thumb {
  background:
    radial-gradient(circle at 35% 40%, #e45545 0 18px, transparent 19px),
    radial-gradient(circle at 66% 62%, #1463ff 0 16px, transparent 17px),
    linear-gradient(160deg, transparent 0 47%, #d9e1ec 48% 52%, transparent 53%),
    #f7f9fc;
}

.thumb[data-visual="modern"] .generated-thumb {
  background: radial-gradient(circle at 50% 50%, #f3c542 0 10px, transparent 11px),
    conic-gradient(from 120deg, #1463ff, #e45545, #f3c542, #00897b, #1463ff);
}

.thumb[data-visual="math"] .generated-thumb {
  background:
    linear-gradient(90deg, rgba(20, 99, 255, 0.12) 1px, transparent 1px),
    linear-gradient(rgba(20, 99, 255, 0.12) 1px, transparent 1px),
    linear-gradient(145deg, transparent 0 44%, #e45545 45% 48%, transparent 49%),
    radial-gradient(circle at 63% 37%, #f3c542 0 6px, transparent 7px),
    #ffffff;
  background-size: 28px 28px, 28px 28px, 100% 100%, 100% 100%, 100% 100%;
}

.thumb[data-visual="tracker"] .generated-thumb {
  background:
    radial-gradient(circle at 30% 38%, #e45545 0 12px, transparent 13px),
    radial-gradient(circle at 52% 53%, #f3c542 0 10px, transparent 11px),
    radial-gradient(circle at 72% 66%, #1463ff 0 12px, transparent 13px),
    linear-gradient(150deg, transparent 0 32%, #00897b 33% 36%, transparent 37%),
    linear-gradient(150deg, transparent 0 54%, #00897b 55% 58%, transparent 59%),
    #ffffff;
}

.thumb[data-visual="external"] .generated-thumb {
  background:
    radial-gradient(circle at 50% 50%, transparent 0 30px, #1463ff 31px 34px, transparent 35px),
    radial-gradient(circle at 50% 50%, transparent 0 56px, #00897b 57px 60px, transparent 61px),
    linear-gradient(90deg, transparent 0 44%, #f3c542 45% 55%, transparent 56%),
    linear-gradient(0deg, transparent 0 44%, #e45545 45% 55%, transparent 56%),
    #ffffff;
}

.thumb[data-visual="phet"] .generated-thumb {
  background:
    radial-gradient(circle at 28% 38%, #f3c542 0 15px, transparent 16px),
    radial-gradient(circle at 50% 50%, #e45545 0 18px, transparent 19px),
    radial-gradient(circle at 72% 40%, #00897b 0 15px, transparent 16px),
    radial-gradient(circle at 42% 72%, #1463ff 0 14px, transparent 15px),
    linear-gradient(135deg, rgba(20, 99, 255, 0.18), rgba(0, 137, 123, 0.16)),
    #ffffff;
}

.card-body {
  display: flex;
  flex-direction: column;
  gap: 10px;
  padding: 16px;
}

.card-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  color: var(--muted);
  font-size: 13px;
  font-weight: 800;
}

.topic {
  color: var(--teal);
}

.resource-card h3 {
  margin: 0;
  font-size: 21px;
  line-height: 1.2;
}

.resource-card p {
  margin: 0;
  color: var(--muted);
  font-weight: 600;
}

.open-label {
  margin-top: auto;
  color: var(--blue);
  font-weight: 800;
}

.site-footer {
  border-top: 1px solid var(--line);
  background: var(--panel);
  padding: 22px clamp(18px, 5vw, 56px);
  color: var(--muted);
  font-weight: 700;
}

.site-footer p {
  margin: 0;
}

@media (max-width: 980px) {
  .filter-row {
    grid-column: 1;
    grid-row: auto;
  }

  .header-actions {
    flex-basis: 100%;
    justify-content: flex-start;
    margin-left: 0;
  }

  .card-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 640px) {
  .site-header,
  .results-heading {
    align-items: stretch;
    flex-direction: column;
  }

  .header-actions {
    width: 100%;
  }

  .icon-button {
    flex: 1 1 auto;
  }

  main {
    width: min(100% - 20px, 100%);
  }

  .hero {
    padding-top: 10px;
  }

  .card-grid {
    grid-template-columns: 1fr;
  }

  .card-link {
    grid-template-rows: 150px 1fr;
  }
}