/* ---------- base ---------- */

:root {
  --bg: #fafaf8;
  --fg: #1c1c1c;
  --muted: #6b6b6b;
  --line: #e3e3df;
  --accent: #1c1c1c;
  --accent-fg: #fafaf8;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #121212;
    --fg: #ececec;
    --muted: #9a9a9a;
    --line: #2c2c2c;
    --accent: #ececec;
    --accent-fg: #121212;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font: 17px/1.6 system-ui, -apple-system, "Segoe UI", sans-serif;
  -webkit-font-smoothing: antialiased;
}

main {
  max-width: 40rem;
  margin: 0 auto;
  padding: 4rem 1.5rem 5rem;
}

h1 {
  font-size: 2rem;
  font-weight: 650;
  letter-spacing: -0.02em;
  margin: 0 0 1rem;
}

.lede { margin: 0 0 0.75rem; }

.tldr {
  margin: 0 0 2.5rem;
  color: var(--muted);
  font-size: 0.95rem;
}

.how {
  margin: 2rem 0;
  color: var(--muted);
  font-size: 0.95rem;
}

/* ---------- palette ---------- */

.palette {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(10.5rem, 1fr));
  gap: 0.75rem;
}

.palette label {
  display: grid;
  grid-template-columns: auto 1fr;
  grid-template-rows: auto auto;
  column-gap: 0.75rem;
  align-items: center;
  padding: 0.8rem 0.9rem;
  border: 1px solid var(--line);
  border-radius: 0.75rem;
  cursor: pointer;
}

.palette .disc {
  grid-row: 1 / 3;
  width: 2.1rem;
  height: 2.1rem;
  border-radius: 50%;
}

.palette strong { font-size: 0.9rem; font-weight: 600; line-height: 1.3; }
.palette small { color: var(--muted); font-size: 0.78rem; line-height: 1.3; }

.d1 { background: radial-gradient(circle at 35% 35%, #23235e, #04040a); }
.d2 { background: radial-gradient(circle at 35% 35%, #571414, #0a0404); }
.d3 { background: #ff2b2b; box-shadow: 0 0 10px 1px rgba(255, 43, 43, 0.7); }
.d4 { background: #22d04a; box-shadow: 0 0 10px 1px rgba(34, 208, 74, 0.7); }
.d5 { background: #ff6a00; }
.d6 { background: #00b43c; }

/* selected card */
#c1:checked ~ main label[for="c1"],
#c2:checked ~ main label[for="c2"],
#c3:checked ~ main label[for="c3"],
#c4:checked ~ main label[for="c4"],
#c5:checked ~ main label[for="c5"],
#c6:checked ~ main label[for="c6"] {
  border-color: var(--fg);
  box-shadow: 0 0 0 1px var(--fg);
}

/* keyboard focus */
#c1:focus-visible ~ main label[for="c1"],
#c2:focus-visible ~ main label[for="c2"],
#c3:focus-visible ~ main label[for="c3"],
#c4:focus-visible ~ main label[for="c4"],
#c5:focus-visible ~ main label[for="c5"],
#c6:focus-visible ~ main label[for="c6"],
#start:focus-visible ~ main .go {
  outline: 2px solid #4c8dff;
  outline-offset: 2px;
}

/* ---------- start button ---------- */

.go {
  display: inline-block;
  padding: 0.7rem 2.4rem;
  border-radius: 99px;
  background: var(--accent);
  color: var(--accent-fg);
  font-weight: 600;
  cursor: pointer;
  user-select: none;
}

/* hide the real inputs, keep them focusable */
input[name="c"], #start {
  position: absolute;
  width: 1px;
  height: 1px;
  opacity: 0;
}

/* ---------- stage ---------- */

/* adapt = colour stared at; reveal = background it switches to */
#c1:checked ~ .stage { --adapt: #ffee00; --reveal: #000000; } /* stygian blue */
#c2:checked ~ .stage { --adapt: #00ffee; --reveal: #000000; } /* stygian red */
#c3:checked ~ .stage { --adapt: #00ffee; --reveal: #ffffff; } /* self-luminous red */
#c4:checked ~ .stage { --adapt: #ff00ff; --reveal: #ffffff; } /* self-luminous green */
#c5:checked ~ .stage { --adapt: #0080ff; --reveal: #ff6a00; } /* hyperbolic orange */
#c6:checked ~ .stage { --adapt: #ff00ff; --reveal: #00b43c; } /* hyperbolic green */

.stage {
  display: none;
  position: fixed;
  inset: 0;
  place-items: center;
  background: var(--adapt);
}

#start:checked ~ .stage {
  display: grid;
  animation: swap 30s step-end forwards;
}

@keyframes swap {
  from { background: var(--adapt); }
  to   { background: var(--reveal); }
}

.stage > * { grid-area: 1 / 1; }

.dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: #000;
  box-shadow: 0 0 0 2px #fff;
}

.hint {
  margin-top: 5.5rem;
  font-size: 0.9rem;
  color: rgba(0, 0, 0, 0.55);
  opacity: 0;
}

#start:checked ~ .stage .hint { animation: fade 30s linear forwards; }

@keyframes fade {
  0%, 15% { opacity: 1; }
  25%, 100% { opacity: 0; }
}

.close {
  place-self: start end;
  padding: 1rem 1.25rem;
  font-size: 1.15rem;
  color: #888;
  cursor: pointer;
  user-select: none;
}

/* ---------- countdown ---------- */

@property --n {
  syntax: "<integer>";
  inherits: true;
  initial-value: 30;
}

.count {
  place-self: end end;
  padding: 1rem 1.25rem;
  font-size: 0.9rem;
  font-variant-numeric: tabular-nums;
  color: rgba(0, 0, 0, 0.4);
}

.count::before {
  counter-reset: n var(--n);
  content: counter(n);
}

#start:checked ~ .stage .count {
  animation: tick 30s linear forwards, vanish 30s step-end forwards;
}

@keyframes tick {
  from { --n: 30; }
  to   { --n: 0; }
}

@keyframes vanish {
  from { opacity: 1; }
  to   { opacity: 0; }
}