:root {
  color-scheme: light;
}

html {
  scroll-behavior: smooth;
  scrollbar-width: none;
}

html::-webkit-scrollbar,
body::-webkit-scrollbar,
*::-webkit-scrollbar {
  width: 0;
  height: 0;
}

body {
  min-height: 100vh;
  background:
    radial-gradient(circle at 18% 22%, rgba(184, 243, 107, 0.24), transparent 16%),
    radial-gradient(circle at top left, rgba(145, 231, 212, 0.55), transparent 24%),
    radial-gradient(circle at 72% 78%, rgba(255, 215, 126, 0.18), transparent 18%),
    radial-gradient(circle at 85% 12%, rgba(122, 198, 255, 0.35), transparent 28%),
    linear-gradient(180deg, #f8fcff 0%, #f3fbf7 48%, #eef8ff 100%);
  scrollbar-width: none;
}

.page-surface {
  position: relative;
  overflow: hidden;
}

.page-surface::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(22, 50, 79, 0.045) 1px, transparent 1px),
    linear-gradient(90deg, rgba(22, 50, 79, 0.045) 1px, transparent 1px);
  background-size: 36px 36px;
  mask-image: linear-gradient(to bottom, rgba(0, 0, 0, 0.25), transparent 88%);
  pointer-events: none;
  z-index: 0;
}

main,
header,
footer {
  position: relative;
  z-index: 1;
}

.iphone-card {
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.92), rgba(244, 252, 255, 0.92));
  border: 1px solid rgba(122, 198, 255, 0.22);
  backdrop-filter: blur(18px);
}

.lesson-frame {
  background: linear-gradient(180deg, rgba(247, 251, 255, 0.98), rgba(227, 243, 251, 0.96));
  border: 1px solid rgba(122, 198, 255, 0.24);
}

.nested-panel {
  background: linear-gradient(180deg, rgba(234, 248, 255, 0.98), rgba(220, 243, 235, 0.96));
  border: 1px solid rgba(122, 198, 255, 0.24);
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.7);
}

.nested-card {
  background: linear-gradient(180deg, rgba(255, 255, 255, 1), rgba(247, 252, 255, 0.98));
  border: 1px solid rgba(122, 198, 255, 0.2);
  box-shadow: 0 12px 28px rgba(72, 120, 151, 0.1);
}

.history-item {
  background: linear-gradient(180deg, rgba(244, 252, 255, 0.96), rgba(235, 250, 243, 0.92));
  border: 1px solid rgba(122, 198, 255, 0.14);
}

.example-chip {
  background: linear-gradient(135deg, rgba(255, 255, 255, 0.96), rgba(240, 249, 255, 0.92));
  border: 1px solid rgba(122, 198, 255, 0.14);
  box-shadow: 0 10px 20px rgba(72, 120, 151, 0.07);
}

.answer-card {
  background: linear-gradient(180deg, rgba(246, 252, 255, 0.96), rgba(233, 248, 255, 0.92));
  border: 1px solid rgba(122, 198, 255, 0.16);
  box-shadow: 0 12px 24px rgba(72, 120, 151, 0.06);
}

.answer-card summary::-webkit-details-marker {
  display: none;
}

.answer-card summary::after {
  content: "+";
  float: right;
  font-size: 1.25rem;
  line-height: 1;
  color: #3f76a4;
}

.answer-card[open] summary::after {
  content: "-";
}

.game-stage {
  background:
    radial-gradient(circle at top right, rgba(184, 243, 107, 0.22), transparent 22%),
    linear-gradient(180deg, rgba(255, 255, 255, 0.95), rgba(243, 250, 255, 0.92));
}

.playful-card {
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.98), rgba(238, 248, 255, 0.94));
  border: 1px solid rgba(122, 198, 255, 0.16);
  box-shadow: 0 12px 22px rgba(72, 120, 151, 0.08);
}

.score-pill {
  background: linear-gradient(135deg, rgba(184, 243, 107, 0.45), rgba(122, 198, 255, 0.18));
  border: 1px solid rgba(117, 167, 44, 0.18);
}

.definition-panel {
  background:
    radial-gradient(circle at top right, rgba(184, 243, 107, 0.18), transparent 28%),
    linear-gradient(180deg, rgba(255, 255, 255, 0.98), rgba(236, 249, 255, 0.94));
  border: 1px solid rgba(122, 198, 255, 0.18);
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.85);
}

.definition-label {
  display: inline-flex;
  padding: 0.45rem 0.8rem;
  border-radius: 9999px;
  background: rgba(122, 198, 255, 0.14);
  color: #2f6b98;
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0.18em;
  text-transform: uppercase;
}

.concept-tile {
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.96), rgba(240, 250, 255, 0.94));
  border: 1px solid rgba(122, 198, 255, 0.16);
  box-shadow: 0 12px 24px rgba(72, 120, 151, 0.08);
}

.numberline {
  position: relative;
  height: 7rem;
}

.numberline-track {
  position: absolute;
  top: 50%;
  left: 0;
  right: 0;
  height: 6px;
  transform: translateY(-50%);
  border-radius: 9999px;
  background: linear-gradient(90deg, rgba(122, 198, 255, 0.65), rgba(184, 243, 107, 0.7));
}

.numberline-point {
  position: absolute;
  top: 50%;
  transform: translate(-50%, -50%);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.6rem;
}

.numberline-point::before {
  content: "";
  width: 18px;
  height: 18px;
  border-radius: 9999px;
  background: #16324f;
  box-shadow: 0 0 0 6px rgba(122, 198, 255, 0.15);
}

.numberline-point span {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 3rem;
  padding: 0.45rem 0.75rem;
  border-radius: 9999px;
  background: rgba(255, 255, 255, 0.94);
  border: 1px solid rgba(122, 198, 255, 0.16);
  font-weight: 800;
  color: #16324f;
}

.quiz-stage {
  background:
    radial-gradient(circle at top right, rgba(184, 243, 107, 0.22), transparent 22%),
    linear-gradient(180deg, rgba(255, 255, 255, 0.96), rgba(243, 250, 255, 0.94));
}

.quiz-card {
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.98), rgba(240, 249, 255, 0.94));
  border: 1px solid rgba(122, 198, 255, 0.18);
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.85);
}

.quiz-option {
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.98), rgba(233, 248, 255, 0.92));
  border: 1px solid rgba(122, 198, 255, 0.18);
  box-shadow: 0 10px 18px rgba(72, 120, 151, 0.08);
  transition: transform 0.2s ease, box-shadow 0.2s ease, opacity 0.2s ease;
}

.quiz-option:hover:not(:disabled) {
  transform: translateY(-2px);
  box-shadow: 0 14px 24px rgba(72, 120, 151, 0.1);
}

.quiz-option:disabled {
  opacity: 0.55;
  cursor: not-allowed;
}

.quiz-result {
  background: rgba(255, 255, 255, 0.82);
  border: 1px solid rgba(122, 198, 255, 0.16);
}

.reveal-up {
  opacity: 0;
  transform: translateY(20px);
  animation: reveal-up 0.7s cubic-bezier(0.19, 1, 0.22, 1) forwards;
}

.delay-1 {
  animation-delay: 0.08s;
}

.delay-2 {
  animation-delay: 0.16s;
}

.delay-3 {
  animation-delay: 0.24s;
}

.mobile-scrollbar {
  scrollbar-width: none;
  -ms-overflow-style: none;
}

.mobile-scrollbar::-webkit-scrollbar {
  display: none;
}

.site-logo {
  width: 2.5rem;
  height: 2.5rem;
  min-width: 2.5rem;
  object-fit: contain;
  object-position: center;
  border-radius: 9999px;
  background: rgba(255, 255, 255, 0.88);
  padding: 0.18rem;
  box-shadow: 0 8px 18px rgba(22, 50, 79, 0.12);
}

.site-wordmark {
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
  line-height: 1;
}

.brand-kicker {
  font-size: 0.72rem;
  letter-spacing: 0.24em;
  text-transform: uppercase;
  color: #4b6b86;
}

.surface-card {
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.96), rgba(243, 250, 255, 0.94));
  border: 1px solid rgba(122, 198, 255, 0.22);
  box-shadow: 0 18px 34px rgba(72, 120, 151, 0.1);
  border-radius: 2.25rem;
}

.surface-subcard {
  background: linear-gradient(180deg, rgba(238, 248, 255, 0.98), rgba(225, 244, 237, 0.96));
  border: 1px solid rgba(122, 198, 255, 0.24);
  border-radius: 2rem;
}

.stat-card {
  background: linear-gradient(180deg, rgba(255, 255, 255, 1), rgba(244, 252, 255, 0.98));
  border: 1px solid rgba(122, 198, 255, 0.18);
  box-shadow: 0 12px 26px rgba(72, 120, 151, 0.08);
  border-radius: 1.75rem;
}

.portrait-frame {
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.98), rgba(232, 246, 255, 0.96));
  border: 1px solid rgba(122, 198, 255, 0.22);
  box-shadow: 0 20px 42px rgba(72, 120, 151, 0.14);
  border-radius: 2.5rem;
}

.portrait-photo {
  width: 100%;
  height: 100%;
  object-fit: cover;
  image-orientation: from-image;
  object-position: center top;
}

.quote-panel {
  background: linear-gradient(135deg, rgba(22, 50, 79, 0.96), rgba(44, 102, 127, 0.94));
  color: #fff;
}

.bootstrap-card.card {
  border: none;
  border-radius: 2rem;
  background: transparent;
}

.bootstrap-card .card-body {
  padding: 1.4rem;
}

.lang-pill {
  min-width: 2.75rem;
  text-align: center;
}

.header-shell {
  max-width: 72rem;
  margin: 0 auto;
}

.header-brand {
  flex: 1 1 auto;
  min-width: 0;
}

.header-actions {
  flex: 0 0 auto;
}

.header-nav {
  flex-wrap: wrap;
}

.nav-pill {
  border-radius: 9999px;
}

.hero-orbit {
  width: 6.5rem;
  max-width: 100%;
  object-fit: contain;
  filter: drop-shadow(0 16px 28px rgba(22, 50, 79, 0.14));
}

.oval-panel {
  border-radius: 2.4rem;
}

.oval-subpanel {
  border-radius: 2rem;
}

.oval-soft {
  border-radius: 1.6rem;
}

.game-card-correct {
  background: linear-gradient(180deg, #d8ff9f, #b8f36b);
  border-color: rgba(117, 167, 44, 0.35);
  box-shadow: 0 14px 24px rgba(117, 167, 44, 0.16);
}

.game-card-wrong {
  background: linear-gradient(180deg, #ffe7e4, #ffd8d6);
  border-color: rgba(214, 115, 108, 0.28);
  box-shadow: 0 14px 24px rgba(214, 115, 108, 0.1);
}

@keyframes reveal-up {
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@media (max-width: 640px) {
  .page-surface::before {
    background-size: 24px 24px;
  }

  .site-logo {
    width: 2rem;
    height: 2rem;
    min-width: 2rem;
  }

  .portrait-photo {
    object-position: center top;
  }

  .brand-kicker {
    font-size: 0.62rem;
    letter-spacing: 0.18em;
  }

  .site-wordmark {
    gap: 0.1rem;
  }

  .header-shell {
    padding-left: 0;
    padding-right: 0;
  }

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

  .header-nav > a {
    justify-content: center;
  }

  .hero-orbit {
    width: 4.5rem;
  }
}