:root {
  --bg: #0a0e14;
  --panel: #111722;
  --panel-light: #1a2230;
  --accent: #2de2a6;
  --accent-dim: #1a9c70;
  --danger: #ff5777;
  --gold: #ffce5c;
  --text: #d7e0ee;
  --muted: #7a8aa0;
  --mono: "SF Mono", "Fira Code", "Cascadia Code", Consolas, monospace;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

body {
  background:
    radial-gradient(circle at 20% 10%, #16202e 0%, var(--bg) 55%);
  color: var(--text);
  font-family: system-ui, -apple-system, sans-serif;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
}

#app { width: 100%; max-width: 680px; }

.screen { display: none; }
.screen.active { display: block; animation: fade 0.4s ease; }
@keyframes fade { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; } }

/* ---------- Terminal panels (start / end) ---------- */
.terminal {
  background: var(--panel);
  border: 1px solid #25324a;
  border-radius: 14px;
  padding: 2.2rem;
  box-shadow: 0 0 60px rgba(45, 226, 166, 0.06), 0 20px 50px rgba(0,0,0,0.5);
}

h1 {
  font-family: var(--mono);
  font-size: 2.4rem;
  letter-spacing: 2px;
  color: var(--accent);
  text-align: center;
}

.subtitle {
  text-align: center;
  color: var(--muted);
  font-family: var(--mono);
  margin: 0.4rem 0 1.6rem;
  letter-spacing: 3px;
  text-transform: uppercase;
  font-size: 0.8rem;
}

.briefing { line-height: 1.6; color: var(--text); margin-bottom: 1.6rem; }
.hl { color: var(--accent); font-weight: 700; }
strong { color: #fff; }

/* glitch title */
.glitch { position: relative; }
.glitch::before, .glitch::after {
  content: attr(data-text);
  position: absolute; left: 0; top: 0; width: 100%;
  overflow: hidden; opacity: 0.7;
}
.glitch::before { color: var(--danger); animation: glitch 3s infinite; clip-path: inset(0 0 60% 0); }
.glitch::after  { color: #4ea1ff; animation: glitch 2.4s infinite reverse; clip-path: inset(60% 0 0 0); }
@keyframes glitch {
  0%, 92%, 100% { transform: translate(0); }
  93% { transform: translate(-3px, 1px); }
  95% { transform: translate(3px, -1px); }
  97% { transform: translate(-2px, 0); }
}

/* difficulty */
.difficulty-pick > p { color: var(--muted); margin-bottom: 0.7rem; font-size: 0.9rem; }
.diff-buttons { display: grid; gap: 0.6rem; margin-bottom: 1.6rem; }
.diff-btn {
  display: flex; flex-direction: column; gap: 2px;
  text-align: left; padding: 0.8rem 1rem;
  background: var(--panel-light);
  border: 1px solid #2a3850; border-radius: 10px;
  color: var(--text); cursor: pointer; transition: all 0.15s;
}
.diff-btn:hover { border-color: var(--accent-dim); }
.diff-btn.selected { border-color: var(--accent); box-shadow: 0 0 0 1px var(--accent); background: #15211c; }
.diff-name { font-weight: 700; font-family: var(--mono); }
.diff-desc { font-size: 0.8rem; color: var(--muted); }

/* buttons */
.big-btn {
  width: 100%; padding: 0.95rem; font-size: 1rem; font-weight: 700;
  font-family: var(--mono); letter-spacing: 1px;
  background: linear-gradient(180deg, var(--accent), var(--accent-dim));
  color: #04130d; border: none; border-radius: 10px; cursor: pointer;
  transition: transform 0.1s, filter 0.15s;
}
.big-btn:hover { filter: brightness(1.1); }
.big-btn:active { transform: scale(0.98); }

.ghost-btn {
  padding: 0.95rem 1.2rem; font-size: 0.9rem; font-family: var(--mono);
  background: transparent; color: var(--muted);
  border: 1px solid #2a3850; border-radius: 10px; cursor: pointer;
}
.ghost-btn:hover { color: var(--gold); border-color: var(--gold); }
.ghost-btn:disabled { opacity: 0.3; cursor: not-allowed; }

/* cheat sheet */
.cheatsheet { margin-top: 1.6rem; border-top: 1px solid #25324a; padding-top: 1rem; }
.cheatsheet summary { cursor: pointer; color: var(--muted); font-family: var(--mono); font-size: 0.85rem; }
.cheat-grid {
  display: grid; grid-template-columns: repeat(8, 1fr); gap: 0.4rem;
  margin: 1rem 0; font-family: var(--mono); font-size: 0.85rem;
}
.cheat-grid span { background: var(--panel-light); padding: 0.4rem 0; text-align: center; border-radius: 6px; }
.cheat-note { color: var(--muted); font-size: 0.85rem; line-height: 1.5; }
code { background: var(--panel-light); padding: 1px 6px; border-radius: 4px; font-family: var(--mono); color: var(--gold); }

/* ---------- HUD ---------- */
.hud {
  display: flex; justify-content: space-between; align-items: center;
  margin-bottom: 1rem; padding: 0 0.4rem;
}
.hud-rooms { display: flex; gap: 0.4rem; }
.room-dot {
  width: 26px; height: 26px; border-radius: 50%;
  display: grid; place-items: center; font-family: var(--mono);
  font-size: 0.8rem; font-weight: 700;
  background: var(--panel-light); color: var(--muted);
  border: 1px solid #2a3850;
}
.room-dot.current { border-color: var(--accent); color: var(--accent); box-shadow: 0 0 8px rgba(45,226,166,0.4); }
.room-dot.done { background: var(--accent-dim); color: #04130d; border-color: var(--accent-dim); }
.hud-right { display: flex; gap: 0.8rem; align-items: center; font-family: var(--mono); }
.hud-timer { font-size: 1.1rem; color: var(--gold); }
.hud-timer.warn { color: var(--danger); animation: pulse 1s infinite; }
@keyframes pulse { 50% { opacity: 0.4; } }
.hud-score { color: var(--accent); font-weight: 700; }

/* ---------- Room ---------- */
.room {
  background: var(--panel);
  border: 1px solid #25324a; border-radius: 14px;
  padding: 2rem; box-shadow: 0 20px 50px rgba(0,0,0,0.5);
}
.room-label { font-family: var(--mono); color: var(--muted); font-size: 0.8rem; letter-spacing: 2px; }
.puzzle-title { font-size: 1.5rem; margin: 0.3rem 0 0.6rem; color: #fff; }
.puzzle-prompt { color: var(--muted); line-height: 1.5; margin-bottom: 1.4rem; }

.puzzle-display {
  font-family: var(--mono); text-align: center;
  background: #060a10; border: 1px solid #1e2940; border-radius: 10px;
  padding: 1.6rem 1rem; margin-bottom: 1.4rem;
}
.big-number { font-size: 2.8rem; font-weight: 700; color: var(--accent); letter-spacing: 4px; }
.display-tag { display: block; color: var(--muted); font-size: 0.8rem; letter-spacing: 2px; margin-top: 0.4rem; text-transform: uppercase; }

/* binary digits with optional place-value labels above each bit */
.bitrow { display: flex; justify-content: center; flex-wrap: wrap; gap: 0.3rem; }
.bitcol { display: flex; flex-direction: column; align-items: center; min-width: 2.1rem; }
.bitcol.nibble-gap { margin-left: 1.1rem; }
.bit { font-size: 2.4rem; font-weight: 700; color: var(--accent); line-height: 1.1; }
.pv { font-size: 0.7rem; color: var(--muted); }

/* standalone place-value strip (hex → binary guide) */
.placevals { display: flex; justify-content: center; flex-wrap: wrap; gap: 0.3rem; margin-top: 1rem; }
.placevals .pv { min-width: 2.1rem; text-align: center; background: var(--panel-light); border-radius: 5px; padding: 0.25rem 0; }
.placevals .pv.nibble-gap { margin-left: 1.1rem; }

.bin-input { letter-spacing: 4px; font-size: 1.6rem; }

/* answer input */
.hex-input {
  width: 100%; font-family: var(--mono); font-size: 2rem; text-align: center;
  text-transform: uppercase; letter-spacing: 8px;
  background: #060a10; color: var(--accent);
  border: 2px solid #2a3850; border-radius: 10px; padding: 0.8rem;
}
.hex-input:focus { outline: none; border-color: var(--accent); }
.input-prefix { color: var(--muted); font-family: var(--mono); }

/* color choices */
.color-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 0.8rem; }
.color-swatch {
  aspect-ratio: 1; border-radius: 12px; cursor: pointer;
  border: 3px solid transparent; transition: transform 0.1s;
}
.color-swatch:hover { transform: scale(1.04); }
.color-swatch.chosen { border-color: #fff; box-shadow: 0 0 0 3px var(--accent); }

/* feedback + controls */
.feedback { min-height: 1.4rem; font-family: var(--mono); margin: 1rem 0; text-align: center; font-weight: 700; }
.feedback.good { color: var(--accent); }
.feedback.bad { color: var(--danger); }
.room-controls { display: flex; gap: 0.8rem; }
.room-controls .big-btn { flex: 1; }
.hint-text {
  margin-top: 1rem; color: var(--gold); font-size: 0.9rem; line-height: 1.6;
  background: rgba(255,206,92,0.08); border-left: 3px solid var(--gold);
  padding: 0.8rem 1rem; border-radius: 0 8px 8px 0; display: none;
}
.hint-text.show { display: block; }

/* end screen stats */
.stats { display: grid; gap: 0.6rem; margin: 1.4rem 0; font-family: var(--mono); }
.stat-row { display: flex; justify-content: space-between; padding: 0.7rem 1rem; background: var(--panel-light); border-radius: 8px; }
.stat-row .val { color: var(--accent); font-weight: 700; }
#end-title { margin-bottom: 0.4rem; }
.win-title { color: var(--accent); }
.lose-title { color: var(--danger); }

@keyframes shake {
  0%,100% { transform: translateX(0); }
  25% { transform: translateX(-8px); }
  75% { transform: translateX(8px); }
}
.shake { animation: shake 0.35s; }