:root {
  --bg: #0b0f1a;
  --surface: #12182a;
  --surface-2: #0d1324;
  --primary: #7cf0ff;
  --accent: #8cffc9;
  --text: #e9eefc;
  --muted: #a9b6d3;
  --ok: #35d086;
  --bad: #ff546a;
}

* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Ubuntu, "Helvetica Neue", Arial, "Noto Sans", "Apple Color Emoji", "Segoe UI Emoji";
  color: var(--text);
  background: radial-gradient(1200px 500px at 20% 0%, #162040 0%, var(--bg) 60%),
              radial-gradient(1000px 600px at 80% 100%, #0f1732 0%, var(--bg) 50%);
}

.hud {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px 22px;
  background: linear-gradient(180deg, rgba(255,255,255,0.04), rgba(255,255,255,0));
  border-bottom: 1px solid rgba(255,255,255,0.06);
}
.brand { font-weight: 700; letter-spacing: 0.5px; }
.stats { display: flex; align-items: center; gap: 18px; }
.lives { font-weight: 600; }
.counter { color: var(--muted); }

.progress {
  width: 200px; height: 8px;
  background: rgba(255,255,255,0.08);
  border-radius: 999px;
  overflow: hidden;
}
.bar { height: 100%; width: 0%; background: linear-gradient(90deg, var(--primary), var(--accent)); }

.screen { display: none; padding: 24px; }
.screen.active { display: block; }

.bullets { color: var(--muted); }
.bullets li { margin: 6px 0; }

.btn {
  padding: 12px 18px;
  border-radius: 10px;
  border: 1px solid rgba(255,255,255,0.12);
  background: var(--surface);
  color: var(--text);
  cursor: pointer;
  transition: transform .08s ease, background .15s ease, box-shadow .15s ease;
}
.btn:hover { transform: translateY(-2px); box-shadow: 0 8px 24px rgba(0,0,0,0.25); }
.btn.primary { background: linear-gradient(180deg, #243059, #1a2446); border-color: rgba(124,240,255,0.4); }

.stage {
  display: grid;
  place-items: center;
  height: calc(100vh - 140px);
  perspective: 1200px;
}

.card {
  position: relative;
  width: min(760px, 92vw);
  min-height: 360px;
  padding: 24px;
  border-radius: 20px;
  background: linear-gradient(170deg, var(--surface), var(--surface-2));
  box-shadow: 0 18px 40px rgba(0,0,0,0.35), inset 0 1px 0 rgba(255,255,255,0.05);
  transform-style: preserve-3d;
  transition: transform .18s ease, box-shadow .2s ease, filter .2s ease;
}
.card h2 { margin-top: 8px; }
.card.glow-correct { box-shadow: 0 18px 40px rgba(53,208,134,0.35), inset 0 1px 0 rgba(255,255,255,0.08); }
.card.glow-wrong { box-shadow: 0 18px 40px rgba(255,84,106,0.35), inset 0 1px 0 rgba(255,255,255,0.08); }

.card-face { position: absolute; inset: 0; padding: 24px; backface-visibility: hidden; }
.card-face.back { transform: rotateY(180deg); display: grid; place-items: center; font-size: 24px; opacity: .9; }

.card.flipped .front { transform: rotateY(180deg); }
.card.flipped .back { transform: rotateY(0deg); }

.options { list-style: none; padding: 0; margin: 18px 0 0; display: grid; gap: 12px; }
.option {
  padding: 14px 16px;
  border-radius: 12px;
  background: rgba(255,255,255,0.06);
  border: 1px solid rgba(255,255,255,0.1);
  cursor: pointer;
  transition: transform .08s ease, background .12s ease;
}
.option:hover { background: rgba(124,240,255,0.12); transform: translateY(-1px); }

#end-screen { text-align: center; }
#end-screen h1 { margin-bottom: 10px; }
#end-screen p { color: var(--muted); margin-bottom: 16px; }