:root {
  --bg: #081019;
  --panel: #102030;
  --panel-hi: #183247;
  --ink: #d8f3ff;
  --accent: #59ffd4;
  --warn: #ffd166;
  --danger: #ff6b6b;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Courier New", Courier, monospace;
  background: radial-gradient(circle at top, #13243a 0%, var(--bg) 55%, #05090f 100%);
  color: var(--ink);
  display: grid;
  place-items: center;
  padding: 24px;
}

.app {
  width: min(860px, 100%);
  background: linear-gradient(180deg, rgba(16, 32, 48, 0.95), rgba(8, 16, 25, 0.95));
  border: 2px solid #2a4f69;
  border-radius: 12px;
  box-shadow: 0 20px 50px rgba(0, 0, 0, 0.45);
  padding: 20px;
}

.topbar h1 {
  margin: 8px 0 2px;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 1px;
}

.topbar p {
  margin: 0 0 16px;
  color: #99c8dd;
}

.back {
  color: var(--warn);
  text-decoration: none;
  font-size: 0.9rem;
}

.hud {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 10px;
  margin-bottom: 14px;
}

.hud div {
  background: var(--panel);
  border: 1px solid #2b5877;
  border-radius: 8px;
  padding: 10px;
  text-align: center;
}

.label {
  display: block;
  color: #89b3c8;
  font-size: 0.8rem;
  margin-bottom: 4px;
  text-transform: uppercase;
}

.controls {
  background: var(--panel);
  border: 1px solid #2b5877;
  border-radius: 8px;
  padding: 12px;
  margin-bottom: 14px;
}

button {
  background: linear-gradient(180deg, #1d4b62, #123344);
  border: 1px solid #4e94b5;
  color: var(--ink);
  font: inherit;
  padding: 10px 14px;
  border-radius: 8px;
  cursor: pointer;
  transition: transform 0.08s ease, filter 0.15s ease;
  margin-right: 8px;
}

button:hover:not(:disabled) { filter: brightness(1.15); }
button:active:not(:disabled) { transform: translateY(1px); }
button:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

#prompt {
  margin-top: 10px;
  color: #b2d8e8;
  min-height: 22px;
}

.pad {
  display: grid;
  grid-template-columns: repeat(3, minmax(70px, 1fr));
  gap: 10px;
  margin-bottom: 16px;
}

.pad button {
  margin: 0;
  min-height: 64px;
  font-size: 1.1rem;
  position: relative;
  background: linear-gradient(180deg, #204f68, #15384a);
}

.pad button small {
  display: block;
  color: #8ab9ce;
  font-size: 0.65rem;
  margin-top: 2px;
}

.pad button.correct {
  border-color: #87ffde;
  box-shadow: 0 0 14px rgba(89, 255, 212, 0.5);
}

.pad button.wrong {
  border-color: var(--danger);
  box-shadow: 0 0 14px rgba(255, 107, 107, 0.45);
}

.log {
  background: var(--panel);
  border: 1px solid #2b5877;
  border-radius: 8px;
  padding: 12px;
}

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

#history {
  margin: 0;
  padding-left: 18px;
  color: #9ed0e5;
  min-height: 70px;
}

@media (max-width: 640px) {
  .hud { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}