:root {
  --bg: #f7fafc;
  --card: #ffffff;
  --muted: #6b7280;
  --accent: #2563eb;
  --accent-2: #7c3aed;
  --radius: 12px;
  --text: #0b1220;
  --correct-background: #ecfdf5;
  --correct-border: #34d399;
  --incorrect-background: #fff1f2;
  --incorrect-border: #fb7185;
  --app-bg-gradient-top: #ffffffcc;
  --app-bg-gradient-bottom: #f8fbffcc;
  --choice-bg-gradient-top: rgba(255, 255, 255, 0.95);
  --choice-bg-gradient-bottom: rgba(250, 250, 252, 0.95);
  --theme-toggle-hover: rgba(37, 99, 235, 0.05);
  --theme-toggle-active: rgba(37, 99, 235, 0.1);
  /* dark theme vars */
  --bg-dark: #181a20;
  --card-dark: #23272f;
  --muted-dark: #6b7280;
  --accent-dark: #3b82f6;
  --accent-2-dark: #6366f1;
  --text-dark: #e5e7eb;
  --correct-background-dark: #1e293b;
  --correct-border-dark: #22d3ee;
  --incorrect-background-dark: #3b1f1f;
  --incorrect-border-dark: #f87171;
  --app-bg-gradient-top-dark: #23272fcc;
  --app-bg-gradient-bottom-dark: #181a20cc;
  --choice-bg-gradient-top-dark: rgba(35, 39, 47, 0.95);
  --choice-bg-gradient-bottom-dark: rgba(24, 26, 32, 0.95);
  --theme-toggle-hover-dark: rgba(59, 130, 246, 0.15);
  --theme-toggle-active-dark: rgba(59, 130, 246, 0.25);
}

.dark-mode {
  --bg: var(--bg-dark);
  --card: var(--card-dark);
  --muted: var(--muted-dark);
  --accent: var(--accent-dark);
  --accent-2: var(--accent-2-dark);
  --text: var(--text-dark);
  --correct-background: var(--correct-background-dark);
  --correct-border: var(--correct-border-dark);
  --incorrect-background: var(--incorrect-background-dark);
  --incorrect-border: var(--incorrect-border-dark);
  color-scheme: dark;
  --app-bg-gradient-top: var(--app-bg-gradient-top-dark);
  --app-bg-gradient-bottom: var(--app-bg-gradient-bottom-dark);
  --choice-bg-gradient-top: var(--choice-bg-gradient-top-dark);
  --choice-bg-gradient-bottom: var(--choice-bg-gradient-bottom-dark);
  --theme-toggle-hover: var(--theme-toggle-hover-dark);
  --theme-toggle-active: var(--theme-toggle-active-dark);
}

/* improve font rendering and base sizing */
html {
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}
body {
  font-size: 16px;
  line-height: 1.45;
}

* {
  box-sizing: border-box;
}

html,
body {
  height: 100%;
  margin: 0;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, "Segoe UI",
    Roboto, Arial;
  color: var(--text);
  background: var(--bg);
}



.app {
  max-width: 920px;
  margin: 28px auto;
  padding: 28px;
  background: linear-gradient(
    180deg,
    var(--app-bg-gradient-top),
    var(--app-bg-gradient-bottom)
  );
  border-radius: calc(var(--radius) + 4px);
  box-shadow: 0 12px 36px rgba(11, 17, 32, 0.06),
    0 3px 8px rgba(124, 58, 237, 0.03);
  border: 1px solid rgba(11, 17, 32, 0.04);
}

.app-header {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.app-header-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-left: 16px;
}

.github-link {
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--accent);
  padding: 6px 10px;
  border-radius: 50%;
  transition: background-color 0.2s, transform 0.2s;
  text-decoration: none;
}
.github-link:hover {
  background: var(--theme-toggle-hover);
  transform: translateY(-2px);
}
.github-link:active {
  background: var(--theme-toggle-active);
  transform: translateY(0);
}
.github-link svg {
  width: 22px;
  height: 22px;
  transition: transform 0.2s;
}
.github-link:hover svg {
  transform: scale(1.1);
}

.theme-toggle {
  background: none;
  border: none;
  cursor: pointer;
  font-size: 1.6rem;
  padding: 6px 10px;
  border-radius: 50%;
  transition: background-color 0.2s;
  color: var(--accent);
  display: flex;
  align-items: center;
  justify-content: center;
}
.theme-toggle:hover {
  background: var(--theme-toggle-hover);
}
.theme-toggle:active {
  background: var(--theme-toggle-active);
}
.theme-icon {
  font-size: 1.4em;
  pointer-events: none;
}

.app-header h1 {
  margin: 0;
  font-size: 1.6rem;
}
.muted {
  color: var(--muted);
}

.card {
  padding: 22px;
  border-radius: 14px;
  margin-top: 16px;
  background: var(--card);
  transition: transform 240ms cubic-bezier(0.2, 0.9, 0.2, 1), box-shadow 240ms;
  will-change: transform;
}

.controls {
  display: flex;
  gap: 12px;
  align-items: center;
  margin-top: 12px;
}
input#seed {
  flex: 1;
  padding: 10px 12px;
  border-radius: 10px;
  border: 1px solid rgba(11, 17, 32, 0.06);
}

.btn {
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  color: #fff;
  padding: 10px 14px;
  border-radius: 12px;
  border: 0;
  cursor: pointer;
  font-weight: 700;
  box-shadow: 0 8px 20px rgba(37, 99, 235, 0.12);
  transition: transform 160ms, box-shadow 160ms, opacity 160ms;
}
.btn:hover {
  transform: translateY(-3px);
}
.btn:active {
  transform: translateY(-1px);
}

.hidden {
  display: none;
}

.quiz-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}
.progress {
  flex-grow: 1;
  height: 10px;
  background: rgba(2, 6, 23, 0.04);
  border-radius: 999px;
  margin-right: 18px;
}
.progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  border-radius: 999px;
  width: 0%;
  transition: width 450ms cubic-bezier(0.2, 0.9, 0.2, 1);
}
.meta {
  display: flex;
  gap: 12px;
  align-items: center;
}

.question {
  margin: 12px 0;
  font-size: 1.05rem;
}
.choices {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.choice {
  padding: 14px;
  border-radius: 12px;
  border: 1px solid rgba(11, 17, 32, 0.04);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 12px;
  background: linear-gradient(
    180deg,
    var(--choice-bg-gradient-top),
    var(--choice-bg-gradient-bottom)
  );
  box-shadow: 0 6px 18px rgba(2, 6, 23, 0.03);
  transition: transform 220ms cubic-bezier(0.2, 0.9, 0.2, 1), box-shadow 220ms,
    background-color 180ms, border-color 180ms, opacity 220ms;
  opacity: 0;
  transform: translateY(6px);
}
.choice.entered {
  opacity: 1;
  transform: translateY(0);
}
.choice:hover {
  box-shadow: 0 12px 30px rgba(124, 58, 237, 0.06);
  transform: translateY(-4px);
}
.choice:focus {
  outline: none;
  box-shadow: 0 0 0 4px rgba(37, 99, 235, 0.12);
  transform: translateY(-2px);
}

.choice.correct {
  background: var(--correct-background);
  border-color: var(--correct-border);
}
.choice.incorrect {
  background: var(--incorrect-background);
  border-color: var(--incorrect-border);
}

.quiz-actions {
  display: flex;
  gap: 10px;
  justify-content: flex-end;
  margin-top: 14px;
}
.app-footer {
  margin-top: 18px;
  color: var(--muted);
  font-size: 0.95rem;
}
.visually-hidden {
  position: absolute !important;
  height: 1px;
  width: 1px;
  overflow: hidden;
  clip: rect(1px, 1px, 1px, 1px);
  white-space: nowrap;
}

.card.animate {
  animation: cardPop 360ms cubic-bezier(0.2, 0.9, 0.2, 1);
  transform-origin: top center;
}
@keyframes cardPop {
  from {
    transform: translateY(6px) scale(0.996);
    opacity: 0.98;
  }
  to {
    transform: translateY(0) scale(1);
    opacity: 1;
  }
}

@media (prefers-reduced-motion: reduce) {
  .progress-bar,
  .choice,
  .card {
    transition: none !important;
    animation: none !important;
  }
}

@media (max-width: 560px) {
  .controls {
    flex-direction: column;
  }
  .quiz-header {
    flex-direction: column;
    align-items: center;
    gap: 12px;
  }
  .quiz-header .progress {
    width: 75%;
    max-width: 320px;
    margin-right: 0;
    margin-bottom: 6px;
  }
  .app {
    margin: 18px;
    padding: 18px;
  }
}