:root {
  --bg0: #05070f;
  --bg1: #0b1226;
  --panel: rgba(22, 30, 55, 0.72);
  --accent: #59c2ff;
  --accent2: #c084fc;
  --accent3: #34f5c5;
  --text: #eaf0ff;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  min-height: 100%;
}

body {
  background:
    radial-gradient(1200px 800px at 20% -10%, #1a2450 0%, transparent 55%),
    radial-gradient(1000px 700px at 90% 10%, #3a1a55 0%, transparent 55%),
    linear-gradient(160deg, var(--bg1), var(--bg0));
  color: var(--text);
  font-family: 'Rajdhani', system-ui, sans-serif;
  display: flex;
  flex-direction: column;
  align-items: center;
  min-height: 100vh;
  user-select: none;
  -webkit-user-select: none;
  overflow-x: hidden;
}

/* Animated scanline / grid overlay for arcade vibe */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  pointer-events: none;
  background-image:
    linear-gradient(rgba(89, 194, 255, 0.04) 1px, transparent 1px),
    linear-gradient(90deg, rgba(89, 194, 255, 0.04) 1px, transparent 1px);
  background-size: 40px 40px;
  mask-image: radial-gradient(ellipse at center, black 40%, transparent 85%);
  animation: drift 30s linear infinite;
  z-index: 0;
}
@keyframes drift {
  to {
    background-position: 400px 400px;
  }
}

header {
  text-align: center;
  padding: 28px 16px 8px;
  z-index: 1;
}

header h1 {
  margin: 0;
  font-family: 'Orbitron', sans-serif;
  font-weight: 900;
  font-size: clamp(2rem, 6vw, 3.4rem);
  letter-spacing: 0.14em;
  background: linear-gradient(90deg, var(--accent), var(--accent2), var(--accent3), var(--accent));
  background-size: 300% 100%;
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  filter: drop-shadow(0 0 18px rgba(89, 194, 255, 0.35));
  animation: hue 6s linear infinite;
}
@keyframes hue {
  to {
    background-position: 300% 0;
  }
}

#rule-desc {
  color: var(--accent);
  font-size: 1rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  opacity: 0.9;
  margin-top: 6px;
}

#hud {
  display: flex;
  gap: 18px;
  margin: 10px 0 18px;
  z-index: 1;
  flex-wrap: wrap;
  justify-content: center;
}

.hud-card {
  background: var(--panel);
  backdrop-filter: blur(10px);
  border: 1px solid rgba(120, 160, 255, 0.18);
  border-radius: 14px;
  padding: 10px 22px;
  min-width: 130px;
  text-align: center;
  box-shadow:
    0 8px 30px rgba(0, 0, 0, 0.45),
    inset 0 1px 0 rgba(255, 255, 255, 0.06);
}
.hud-card .label {
  display: block;
  font-size: 0.72rem;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  opacity: 0.55;
}
.hud-card .value {
  font-family: 'Orbitron', sans-serif;
  font-weight: 700;
  font-size: 1.7rem;
  line-height: 1.2;
  color: #fff;
}
#score {
  transition: transform 0.12s ease;
}
.bump {
  transform: scale(1.28);
}

#board-wrap {
  position: relative;
  background: linear-gradient(180deg, rgba(30, 42, 78, 0.5), rgba(10, 16, 32, 0.6));
  border-radius: 22px;
  padding: 14px;
  border: 1px solid rgba(120, 160, 255, 0.22);
  box-shadow:
    0 20px 60px rgba(0, 0, 0, 0.6),
    0 0 60px rgba(89, 194, 255, 0.12),
    inset 0 1px 0 rgba(255, 255, 255, 0.08);
  z-index: 1;
}
/* Neon border sweep */
#board-wrap::after {
  content: '';
  position: absolute;
  inset: -2px;
  border-radius: 24px;
  padding: 2px;
  background: linear-gradient(
    120deg,
    var(--accent),
    transparent 30%,
    transparent 70%,
    var(--accent2)
  );
  -webkit-mask:
    linear-gradient(#000 0 0) content-box,
    linear-gradient(#000 0 0);
  -webkit-mask-composite: xor;
  mask-composite: exclude;
  opacity: 0.6;
  animation: hue 6s linear infinite;
  pointer-events: none;
}

canvas {
  display: block;
  touch-action: none;
  border-radius: 12px;
}

#indicator {
  margin-top: 16px;
  min-height: 1.6rem;
  font-family: 'Orbitron', sans-serif;
  font-size: 1.25rem;
  letter-spacing: 0.06em;
  text-align: center;
  z-index: 1;
  transition: transform 0.15s ease;
}
#indicator.valid {
  color: #7dffb0;
  text-shadow: 0 0 18px rgba(80, 255, 150, 0.7);
  animation: pop 0.35s ease;
}
#indicator.invalid {
  color: #ff6b8a;
  text-shadow: 0 0 16px rgba(255, 80, 110, 0.6);
  animation: shakeText 0.35s ease;
}
@keyframes pop {
  0% {
    transform: scale(0.6);
    opacity: 0;
  }
  60% {
    transform: scale(1.15);
  }
  100% {
    transform: scale(1);
  }
}
@keyframes shakeText {
  0%,
  100% {
    transform: translateX(0);
  }
  25% {
    transform: translateX(-8px);
  }
  75% {
    transform: translateX(8px);
  }
}

/* ---- Config menu ---- */
#config-menu {
  position: relative;
  background: var(--panel);
  backdrop-filter: blur(16px);
  border-radius: 20px;
  padding: 30px 28px;
  border: 1px solid rgba(120, 160, 255, 0.22);
  box-shadow:
    0 24px 70px rgba(0, 0, 0, 0.6),
    0 0 50px rgba(120, 100, 255, 0.15);
  width: 380px;
  max-width: 92vw;
  z-index: 1;
  margin-top: 10px;
}
#config-menu h2 {
  margin: 0 0 20px;
  font-family: 'Orbitron', sans-serif;
  font-size: 1.3rem;
  letter-spacing: 0.12em;
  text-align: center;
  background: linear-gradient(90deg, var(--accent), var(--accent2));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.cfg-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 14px;
  gap: 12px;
}
.cfg-row label {
  opacity: 0.85;
  font-size: 0.98rem;
  letter-spacing: 0.03em;
}
.cfg-row input,
.cfg-row select {
  background: rgba(10, 16, 32, 0.7);
  color: var(--text);
  border: 1px solid rgba(120, 160, 255, 0.28);
  border-radius: 8px;
  padding: 8px 10px;
  font-family: 'Rajdhani', sans-serif;
  font-size: 0.98rem;
  transition:
    border-color 0.2s,
    box-shadow 0.2s;
}
.cfg-row input:focus,
.cfg-row select:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(89, 194, 255, 0.2);
}
.cfg-row input[type='number'] {
  width: 80px;
}
.cfg-row select {
  max-width: 200px;
}
button.primary,
button.secondary {
  font-family: 'Orbitron', sans-serif;
  letter-spacing: 0.1em;
  border: none;
  border-radius: 12px;
  padding: 14px 22px;
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  width: 100%;
  margin-top: 12px;
  transition:
    transform 0.12s ease,
    box-shadow 0.2s ease,
    filter 0.2s;
}
button.primary {
  color: #05070f;
  background: linear-gradient(120deg, var(--accent), var(--accent3));
  box-shadow: 0 10px 30px rgba(52, 245, 197, 0.35);
}
button.primary:hover {
  transform: translateY(-2px) scale(1.02);
  filter: brightness(1.08);
  box-shadow: 0 14px 40px rgba(52, 245, 197, 0.5);
}
button.primary:active {
  transform: translateY(0) scale(0.99);
}
button.secondary {
  color: var(--text);
  background: rgba(30, 42, 78, 0.8);
  border: 1px solid rgba(120, 160, 255, 0.3);
  width: auto;
}
button.secondary:hover {
  transform: translateY(-2px);
  box-shadow: 0 10px 26px rgba(0, 0, 0, 0.4);
}