:root {
  --bg: #07111f;
  --panel: rgba(12, 22, 42, 0.94);
  --border: rgba(125, 211, 252, 0.16);
  --text: #ecf4ff;
  --muted: #99a8cf;
  --accent: #7dd3fc;
  --green: #34d399;
  --blue: #60a5fa;
  --danger: #fb7185;
}

* { box-sizing: border-box; }
html, body {
  overscroll-behavior: none;
}
body {
  margin: 0;
  font-family: "Microsoft YaHei", "PingFang SC", sans-serif;
  color: var(--text);
  background: radial-gradient(circle at top, #17315f 0%, var(--bg) 40%), var(--bg);
}
button {
  font: inherit;
}
.page {
  width: min(1200px, calc(100% - 32px));
  margin: 0 auto;
  padding: 24px 0 32px;
}
.panel {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 22px;
  box-shadow: 0 18px 50px rgba(0, 0, 0, 0.35);
}
.subtitle,
.menu-tip,
.score-hint,
.status-label,
.info-block li,
.info-block p {
  color: var(--muted);
}
.back-link {
  color: var(--accent);
  text-decoration: none;
}
.primary-button,
.ghost-button,
.mode-button {
  border: 0;
  border-radius: 14px;
  cursor: pointer;
  transition: transform 0.15s ease, opacity 0.15s ease, background 0.15s ease;
}
.primary-button:hover,
.ghost-button:hover,
.mode-button:hover {
  transform: translateY(-1px);
}
.primary-button {
  background: var(--accent);
  color: #08101f;
  font-weight: 700;
  padding: 12px 16px;
}
.ghost-button {
  background: transparent;
  color: var(--text);
  border: 1px solid rgba(255, 255, 255, 0.12);
  padding: 11px 16px;
}
.layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 300px;
  gap: 18px;
  align-items: stretch;
}
.board-panel {
  padding: 18px;
  display: flex;
  flex-direction: column;
  justify-content: center;
}
#board {
  width: 100%;
  max-width: 720px;
  aspect-ratio: 1;
  display: block;
  margin: 0 auto;
  background: #050b14;
  border-radius: 18px;
  border: 1px solid rgba(255,255,255,0.08);
}
.status-bar {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin-top: 16px;
  flex-wrap: wrap;
}
.sidebar {
  padding: 18px;
  display: flex;
  flex-direction: column;
  gap: 16px;
}
.side-top h1 {
  margin: 8px 0 6px;
  font-size: 28px;
}
.actions {
  display: flex;
  gap: 12px;
  align-items: flex-start;
  flex-wrap: wrap;
  margin-top: 14px;
}
.score-card,
.info-block {
  border-radius: 18px;
  padding: 16px;
  background: rgba(255,255,255,0.03);
  border: 1px solid rgba(255,255,255,0.06);
}
.snake-one { box-shadow: inset 0 0 0 1px rgba(52, 211, 153, 0.14); }
.snake-two { box-shadow: inset 0 0 0 1px rgba(96, 165, 250, 0.14); }
.score-title {
  font-size: 14px;
  color: var(--muted);
}
.score-value {
  font-size: 42px;
  font-weight: 800;
  margin: 8px 0 6px;
}
.info-block h2 {
  margin-top: 0;
  font-size: 18px;
}
.info-block ul {
  margin: 12px 0 0;
  padding-left: 18px;
  line-height: 1.8;
}
.overlay {
  position: fixed;
  inset: 0;
  background: rgba(3, 7, 15, 0.72);
  backdrop-filter: blur(8px);
  display: none;
  align-items: center;
  justify-content: center;
  padding: 20px;
}
.overlay.show {
  display: flex;
}
.modal {
  width: min(720px, 100%);
  padding: 28px;
}
.modal h2 {
  margin-top: 0;
  font-size: 28px;
}
.mode-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 16px;
  margin: 18px 0;
}
.mode-button {
  padding: 20px;
  text-align: left;
  background: linear-gradient(135deg, rgba(23,49,95,0.95), rgba(8,16,31,0.95));
  color: var(--text);
  border: 1px solid rgba(125, 211, 252, 0.22);
}
.mode-button span {
  display: block;
  font-size: 20px;
  font-weight: 700;
  margin-bottom: 8px;
}
.mode-button small {
  color: var(--muted);
  line-height: 1.6;
}

@media (max-width: 920px) {
  .layout {
    grid-template-columns: 1fr;
  }
}