:root {
  --bg: #181c1f;
  --bg-alt: #23282d;
  --ink: #f5f7fa;
  --muted: #b0bac3;
  --accent: #ff7a4d;
  --accent-alt: #4dd0e1;
  --card: #23282d;
  --ok: #4caf50;
  --bad: #ff5252;
  --ring: #4dd0e1;
  --shadow: 0 12px 35px rgba(0, 0, 0, 0.32);
  --font-display: "Franklin Gothic Medium", "Trebuchet MS", sans-serif;
  --font-body: "Gill Sans", "Candara", sans-serif;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font-body);
  color: var(--ink);
  background:
    radial-gradient(circle at 90% 10%, rgba(255, 122, 77, 0.10), transparent 35%),
    radial-gradient(circle at 12% 78%, rgba(77, 208, 225, 0.10), transparent 40%),
    linear-gradient(135deg, var(--bg), var(--bg-alt));
}

.app-shell {
  width: min(920px, 94vw);
  margin: 1.5rem auto;
  padding: 1.2rem;
  border: 2px solid rgba(77, 208, 225, 0.13);
  border-radius: 22px;
  background: rgba(35, 40, 45, 0.92);
  backdrop-filter: blur(2px);
}

.app-header h1 {
  margin: 0.1rem 0;
  font-family: var(--font-display);
  font-size: clamp(1.5rem, 3vw, 2.2rem);
  letter-spacing: 0.03em;
  text-transform: uppercase;
}

.kicker {
  margin: 0;
  color: var(--accent-alt);
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.subtitle {
  margin: 0.35rem 0 1.1rem;
  color: var(--muted);
}

.controls {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  align-items: center;
}

.mode-picker {
  font-weight: 700;
}

select,
button {
  font: inherit;
  border-radius: 10px;
  border: 2px solid rgba(77, 208, 225, 0.18);
  padding: 0.55rem 0.85rem;
  background: #23282d;
  color: var(--ink);
}

button {
  cursor: pointer;
  transition: transform 120ms ease, border-color 120ms ease, background 120ms ease;
}

button:hover:not(:disabled) {
  transform: translateY(-1px);
  border-color: rgba(77, 208, 225, 0.4);
}

button:focus-visible,
select:focus-visible {
  outline: 3px solid var(--ring);
  outline-offset: 2px;
}

button:disabled {
  cursor: not-allowed;
  opacity: 0.55;
}

.stats {
  margin-top: 1rem;
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 0.5rem;
}

.stats p {
  margin: 0;
  background: rgba(35, 40, 45, 0.85);
  border: 1px solid rgba(77, 208, 225, 0.13);
  border-radius: 10px;
  text-align: center;
  padding: 0.55rem;
  color: var(--ink);
}

.flashcard-wrap {
  margin-top: 1rem;
  perspective: 1400px;
}

.flashcard {
  min-height: 520px;
  border-radius: 20px;
  position: relative;
  transform-style: preserve-3d;
  transition: transform 320ms ease;
  box-shadow: var(--shadow);
}

.flashcard[data-flipped="true"] {
  transform: rotateY(180deg);
}

.face {
  position: absolute;
  inset: 0;
  border-radius: 20px;
  padding: 1.2rem;
  overflow: hidden;
  backface-visibility: hidden;
  border: 3px solid rgba(77, 208, 225, 0.08);
  display: grid;
  align-content: start;
  gap: 0.5rem;
}

.face-front {
  background: linear-gradient(165deg, #23282d 0%, #181c1f 80%);
}

.face-back {
  background: linear-gradient(165deg, #23282d 0%, #181c1f 80%);
  transform: rotateY(180deg);
}

.face-label {
  margin: 0;
  font-weight: 700;
  color: var(--accent-alt);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

h2 {
  margin: 0;
  line-height: 1.15;
  font-family: var(--font-display);
  font-size: clamp(1.45rem, 4vw, 2.3rem);
}

.hint,
.summary,
.rule-ref {
  margin: 0;
  color: var(--muted);
}

.official-meta {
  margin: 0;
  color: var(--muted);
}

.icon-box {
  width: 100%;
  min-height: clamp(240px, 42vh, 380px);
  border-radius: 14px;
  border: 2px dashed rgba(77, 208, 225, 0.18);
  background: rgba(35, 40, 45, 0.85);
  display: grid;
  place-items: center;
  padding: 0.5rem;
  overflow: hidden;
  contain: layout paint;
}

#signal-icon {
  --signal-max-width: 640px;
  --signal-max-height: 420px;
  max-width: min(100%, var(--signal-max-width));
  max-height: min(100%, var(--signal-max-height));
  width: auto;
  height: auto;
  object-fit: contain;
  cursor: zoom-in;
  transition: transform 180ms ease, opacity 120ms ease;
  transform-origin: center center;
  touch-action: manipulation;
  opacity: 0;
  visibility: hidden;
}

.flashcard[data-flipped="true"] #signal-icon {
  opacity: 1;
  visibility: visible;
}

#signal-icon.zoomed {
  transform: scale(1.6);
  cursor: zoom-out;
  will-change: transform;
}

.actions {
  margin-top: 1rem;
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 0.55rem;
}

#correct-btn {
  background: #234d2b;
  border-color: rgba(76, 175, 80, 0.4);
  color: #b6f7c1;
}

#incorrect-btn {
  background: #4d2323;
  border-color: rgba(255, 82, 82, 0.35);
  color: #ffd6d6;
}

.status {
  min-height: 1.5rem;
  margin: 0.8rem 0 0;
  font-weight: 700;
}

.app-footer {
  margin-top: 1rem;
  color: var(--muted);
  font-size: 0.95rem;
}

kbd {
  border: 1px solid rgba(77, 208, 225, 0.18);
  border-radius: 4px;
  padding: 0.05rem 0.35rem;
  background: rgba(35, 40, 45, 0.85);
  color: var(--ink);
}

a {
  color: var(--accent-alt);
  text-decoration: underline;
}

a:visited {
  color: #b399d6;
}

a:hover:not(:visited) {
  color: #5ce7f5;
}

@media (max-width: 780px) {
  .stats {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

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

  #flip-btn {
    grid-column: 1 / -1;
  }

  .flashcard {
    min-height: 560px;
  }
}

@media (max-width: 480px) {
  .icon-box {
    min-height: 230px;
  }

  #signal-icon {
    --signal-max-width: min(520px, 92vw);
  }

  #signal-icon.zoomed {
    transform: scale(1.35);
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}