:root {
  --bg: #0b1020;
  --bg-soft: #131a30;
  --panel: #161e36;
  --panel-2: #1d2745;
  --text: #eef2ff;
  --muted: #9aa6c8;
  --line: rgba(255, 255, 255, 0.09);
  --accent: #7cf3c0;
  --accent-2: #5ad1ff;
  --danger: #ff8f9c;
  --board: #0e1527;
  --grid: rgba(255, 255, 255, 0.045);
  --snake: #7cf3c0;
  --snake-head: #b9ffe3;
  --food: #ff8f9c;
  --shadow: 0 18px 50px rgba(0, 0, 0, 0.35);
  --radius: 16px;
}
html[data-theme="light"] {
  --bg: #f4f7fb;
  --bg-soft: #eaf0f8;
  --panel: #ffffff;
  --panel-2: #f1f5fb;
  --text: #101828;
  --muted: #5a6884;
  --line: rgba(16, 24, 40, 0.1);
  --accent: #0f9f6e;
  --accent-2: #1273c4;
  --danger: #c2334a;
  --board: #eef4fb;
  --grid: rgba(16, 24, 40, 0.06);
  --snake: #0f9f6e;
  --snake-head: #0a7d56;
  --food: #c2334a;
  --shadow: 0 16px 40px rgba(16, 24, 40, 0.12);
}
* { box-sizing: border-box; }
html, body { margin: 0; min-height: 100%; }
body {
  background: radial-gradient(1200px 600px at 15% -10%, rgba(90, 209, 255, 0.16), transparent 60%),
              radial-gradient(900px 500px at 105% 5%, rgba(124, 243, 192, 0.14), transparent 55%),
              var(--bg);
  color: var(--text);
  font: 15px/1.5 -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  -webkit-font-smoothing: antialiased;
}
h1, h2, p { margin: 0; }
button, input { font: inherit; }

.app { max-width: 1120px; margin: 0 auto; padding: 24px 20px 32px; }
.topbar { display: flex; align-items: center; justify-content: space-between; gap: 16px; margin-bottom: 20px; }
.brand { display: flex; align-items: center; gap: 12px; }
.brand-mark { width: 38px; height: 38px; border-radius: 12px; background: linear-gradient(140deg, var(--accent), var(--accent-2)); box-shadow: var(--shadow); position: relative; }
.brand-mark::after { content: ""; position: absolute; inset: 9px; border-radius: 8px; border: 2px solid rgba(11, 16, 32, 0.55); }
.brand h1 { font-size: 20px; letter-spacing: 0.02em; }
.brand-sub { color: var(--muted); font-size: 12px; }
.identity { display: flex; align-items: center; gap: 10px; min-width: 0; }
.nick { max-width: 160px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; font-weight: 600; }
.chip { font-size: 12px; color: var(--muted); border: 1px solid var(--line); border-radius: 999px; padding: 4px 10px; background: var(--panel); }

.layout { display: grid; grid-template-columns: minmax(0, 1.5fr) minmax(280px, 1fr); gap: 20px; align-items: start; }
.board-wrap { position: relative; background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius); padding: 14px; box-shadow: var(--shadow); }
canvas { display: block; width: 100%; height: auto; aspect-ratio: 1 / 1; border-radius: 10px; background: var(--board); touch-action: none; }
.overlay { position: absolute; inset: 14px; display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 10px; text-align: center; padding: 24px; border-radius: 10px; background: color-mix(in srgb, var(--board) 82%, transparent); backdrop-filter: blur(3px); }
.overlay[hidden] { display: none; }
.overlay h2 { font-size: 22px; }
.overlay p { color: var(--muted); max-width: 26em; }

.panel { display: flex; flex-direction: column; gap: 16px; }
.stats { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 10px; }
.stat { background: var(--panel); border: 1px solid var(--line); border-radius: 12px; padding: 12px; }
.stat-label { display: block; color: var(--muted); font-size: 12px; margin-bottom: 4px; }
.stat strong { font-size: 20px; font-variant-numeric: tabular-nums; }
.form, .controls { background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius); padding: 16px; }
.form label { display: block; font-size: 13px; color: var(--muted); margin-bottom: 8px; }
.form-row { display: flex; gap: 8px; }
.form-row input { flex: 1; min-width: 0; background: var(--panel-2); color: var(--text); border: 1px solid var(--line); border-radius: 10px; padding: 10px 12px; }
.form-row input:focus-visible, .btn:focus-visible, .dpad-btn:focus-visible { outline: 2px solid var(--accent-2); outline-offset: 2px; }
.hint { color: var(--muted); font-size: 12px; margin-top: 10px; }
.form-status { color: var(--accent); font-size: 12px; min-height: 18px; margin-top: 6px; }
.form-status.error { color: var(--danger); }
.btn { appearance: none; border: 1px solid var(--line); background: var(--panel-2); color: var(--text); border-radius: 10px; padding: 9px 14px; cursor: pointer; transition: transform 0.12s ease, background 0.12s ease; }
.btn:hover:not(:disabled) { background: color-mix(in srgb, var(--panel-2) 80%, var(--accent)); }
.btn:active:not(:disabled) { transform: translateY(1px); }
.btn:disabled { opacity: 0.55; cursor: not-allowed; }
.btn-primary { background: linear-gradient(140deg, var(--accent), var(--accent-2)); color: #08101f; border-color: transparent; font-weight: 700; }
.control-row { display: flex; gap: 8px; margin-bottom: 14px; }
.control-row .btn { flex: 1; }
.dpad { display: grid; grid-template-columns: repeat(3, 56px); grid-template-rows: repeat(2, 48px); gap: 8px; justify-content: center; }
.dpad-btn { background: var(--panel-2); color: var(--text); border: 1px solid var(--line); border-radius: 12px; cursor: pointer; font-size: 15px; }
.dpad-btn:active { background: color-mix(in srgb, var(--panel-2) 70%, var(--accent)); }
.dpad-up { grid-column: 2; grid-row: 1; }
.dpad-left { grid-column: 1; grid-row: 2; }
.dpad-down { grid-column: 2; grid-row: 2; }
.dpad-right { grid-column: 3; grid-row: 2; }
.footer { display: flex; justify-content: space-between; gap: 12px; color: var(--muted); font-size: 12px; margin-top: 18px; flex-wrap: wrap; }

.screen { position: fixed; inset: 0; display: grid; place-items: center; padding: 24px; background: var(--bg); z-index: 20; }
.screen[hidden] { display: none; }
.screen-card { max-width: 460px; width: 100%; text-align: center; background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius); padding: 32px 24px; box-shadow: var(--shadow); }
.screen-card h1 { font-size: 20px; margin-bottom: 10px; }
.screen-card p { color: var(--muted); margin-bottom: 18px; white-space: pre-wrap; }
.loader { width: 34px; height: 34px; margin: 0 auto 16px; border-radius: 50%; border: 3px solid var(--line); border-top-color: var(--accent); animation: spin 0.9s linear infinite; }
.screen.error .loader { display: none; }
.screen.error h1 { color: var(--danger); }
@keyframes spin { to { transform: rotate(360deg); } }

@media (max-width: 820px) {
  .layout { grid-template-columns: minmax(0, 1fr); }
  .app { padding: 16px 12px 24px; }
  .board-wrap { padding: 10px; }
  .overlay { inset: 10px; }
  .stats { grid-template-columns: repeat(3, minmax(0, 1fr)); }
}
@media (max-width: 380px) {
  .brand h1 { font-size: 18px; }
  .nick { max-width: 110px; }
  .dpad { grid-template-columns: repeat(3, 48px); grid-template-rows: repeat(2, 44px); }
  .stat { padding: 10px; }
  .stat strong { font-size: 17px; }
}
@media (prefers-reduced-motion: reduce) {
  .loader { animation: none; }
  .btn { transition: none; }
}