:root {
  --bg: #090a12;
  --panel: #11162a;
  --line: #334063;
  --ink: #eef1ff;
  --muted: #97a2c8;
  --amber: #ffc165;
  --amber-hi: #ffe2b0;
  --danger: #ff7a94;
  --ok: #80ffb2;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  background:
    radial-gradient(circle at 15% -10%, rgba(255, 180, 95, 0.14), transparent 45%),
    radial-gradient(circle at 85% 0%, rgba(112, 175, 255, 0.12), transparent 40%),
    linear-gradient(180deg, #0d1020, var(--bg));
  color: var(--ink);
  font-family: "Courier New", Courier, monospace;
  display: grid;
  place-items: center;
  padding: 22px;
}

.app {
  width: min(900px, 100%);
  background: linear-gradient(180deg, rgba(17, 22, 42, 0.95), rgba(10, 13, 25, 0.95));
  border: 2px solid var(--line);
  border-radius: 12px;
  box-shadow: 0 20px 55px rgba(0, 0, 0, 0.5);
  padding: 20px;
}

.back {
  color: #f9dc9a;
  text-decoration: none;
  font-size: 0.9rem;
}

.topbar h1 {
  margin: 8px 0 4px;
  color: var(--amber);
  text-transform: uppercase;
  letter-spacing: 1px;
}

.topbar p {
  margin: 0 0 14px;
  color: #b8c1e3;
}

.hud {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 10px;
}

.hud div {
  background: #131a33;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 10px;
  text-align: center;
}

.label {
  display: block;
  font-size: 0.74rem;
  color: var(--muted);
  text-transform: uppercase;
  margin-bottom: 4px;
}

.lock-screen {
  margin-top: 12px;
  border: 1px solid #4f5d84;
  border-radius: 10px;
  background: linear-gradient(180deg, #171f3d, #0e1430);
  padding: 16px;
}

.tube-row {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 10px;
}

.tube {
  border: 1px solid #6b7499;
  border-radius: 9px;
  background: radial-gradient(circle at 50% 15%, rgba(255, 210, 160, 0.25), rgba(26, 24, 30, 0.95));
  min-height: 78px;
  display: grid;
  place-items: center;
  font-size: clamp(1.8rem, 5vw, 2.3rem);
  color: var(--amber);
  text-shadow: 0 0 10px rgba(255, 180, 88, 0.6), 0 0 20px rgba(255, 180, 88, 0.25);
}

.tube.active {
  border-color: #ffe2b0;
  box-shadow: 0 0 0 1px rgba(255, 226, 176, 0.45), inset 0 0 25px rgba(255, 178, 95, 0.16);
}

.hint {
  margin-top: 12px;
  color: #d3dbf7;
  min-height: 1.2rem;
}

.keypad {
  margin-top: 12px;
  display: grid;
  gap: 10px;
}

.digit-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 8px;
}

button {
  font: inherit;
  color: var(--ink);
  border: 1px solid #5981a7;
  border-radius: 8px;
  padding: 11px 10px;
  background: linear-gradient(180deg, #2a4f73, #1a3551);
  cursor: pointer;
  transition: transform 0.08s ease, filter 0.15s ease;
}

button:hover:not(:disabled) { filter: brightness(1.12); }
button:active:not(:disabled) { transform: translateY(1px); }
button:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

button.ghost {
  background: linear-gradient(180deg, #2d3145, #1d2338);
  border-color: #566180;
}

.actions {
  display: grid;
  grid-template-columns: 1fr 1fr 1.3fr;
  gap: 8px;
}

.rules,
.log {
  margin-top: 12px;
  background: #121a33;
  border: 1px solid var(--line);
  border-radius: 9px;
  padding: 12px;
}

.rules h2,
.log h2 {
  margin: 0 0 8px;
  color: var(--amber-hi);
  font-size: 1rem;
}

.rules ul {
  margin: 0;
  padding-left: 18px;
  color: #ccd6fa;
}

table {
  width: 100%;
  border-collapse: collapse;
}

th,
td {
  border-bottom: 1px dashed #344264;
  padding: 8px 6px;
  text-align: left;
}

th {
  text-transform: uppercase;
  font-size: 0.76rem;
  color: #9dadde;
}

.good { color: var(--ok); }
.bad { color: var(--danger); }

.controls {
  margin-top: 10px;
}

@media (max-width: 760px) {
  .hud { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .digit-grid { grid-template-columns: repeat(4, minmax(0, 1fr)); }
  .actions { grid-template-columns: 1fr; }
}