:root {
  --bg: #f4f7f8;
  --panel: #ffffff;
  --line: #d7e0e4;
  --line-strong: #b8c6cd;
  --text: #1f2933;
  --muted: #5b6975;
  --primary: #0f766e;
  --primary-soft: #e0f2ef;
  --danger: #b42318;
  --danger-soft: #fff1f0;
  --board-bg: #f8fafb;
  --snake: #0f766e;
  --snake-head: #115e59;
  --food: #dc2626;
  --shadow: 0 12px 28px rgba(31, 41, 51, 0.08);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: linear-gradient(180deg, #eef4f5 0%, #f8fafb 100%);
  color: var(--text);
  font-family: "Noto Sans JP", "Hiragino Sans", "Yu Gothic", sans-serif;
}

.page {
  width: min(1040px, calc(100% - 24px));
  margin: 0 auto;
  padding: 20px 0 40px;
}

.back-link {
  display: inline-flex;
  margin-bottom: 16px;
  color: var(--primary);
  text-decoration: none;
  font-weight: 700;
}

.back-link:hover,
.back-link:focus-visible {
  text-decoration: underline;
}

.hero,
.panel {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 24px;
  box-shadow: var(--shadow);
}

.hero {
  padding: 28px;
}

.hero-badge {
  display: inline-flex;
  padding: 6px 12px;
  border-radius: 999px;
  background: var(--primary-soft);
  color: var(--primary);
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.04em;
}

.hero h1 {
  margin: 14px 0 10px;
  font-size: clamp(1.8rem, 4vw, 2.6rem);
  line-height: 1.25;
}

.hero-text,
.panel-heading p,
.help-box li {
  margin: 0;
  color: var(--muted);
  line-height: 1.8;
}

.layout {
  display: grid;
  grid-template-columns: minmax(0, 1.1fr) minmax(280px, 0.75fr);
  gap: 20px;
  margin-top: 20px;
  align-items: start;
}

.panel {
  padding: 22px;
}

.panel-heading {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  align-items: flex-start;
  margin-bottom: 16px;
}

.panel-heading h2,
.help-box h2 {
  margin: 0 0 8px;
  font-size: 1.1rem;
}

.status-chip {
  min-width: 86px;
  padding: 8px 12px;
  border-radius: 999px;
  background: #f3f6f7;
  border: 1px solid var(--line);
  color: var(--muted);
  text-align: center;
  font-size: 0.82rem;
  font-weight: 800;
  letter-spacing: 0.06em;
}

.status-chip.playing {
  background: var(--primary-soft);
  border-color: #bfe5de;
  color: var(--primary);
}

.status-chip.paused {
  background: #fff5e8;
  border-color: #f1d4a6;
  color: #8a5a00;
}

.status-chip.over {
  background: var(--danger-soft);
  border-color: #f0b1aa;
  color: var(--danger);
}

.board {
  display: grid;
  grid-template-columns: repeat(16, minmax(0, 1fr));
  gap: 3px;
  width: min(100%, 560px);
  aspect-ratio: 1 / 1;
  padding: 12px;
  border-radius: 20px;
  background: #dde6ea;
  border: 1px solid var(--line);
  user-select: none;
  touch-action: manipulation;
  outline: none;
  margin: 0 auto;
  align-content: stretch;
}

.cell {
  aspect-ratio: 1;
  border-radius: 6px;
  background: var(--board-bg);
}

.cell.snake {
  background: var(--snake);
}

.cell.head {
  background: var(--snake-head);
}

.cell.food {
  background: var(--food);
}

.controls-row {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  margin-top: 16px;
}

.game-panel {
  display: flex;
  flex-direction: column;
}

.action-button,
.dpad-button {
  appearance: none;
  border: 1px solid var(--line-strong);
  background: #fff;
  color: var(--text);
  border-radius: 999px;
  font: inherit;
  font-weight: 700;
  cursor: pointer;
}

.action-button {
  padding: 12px 16px;
}

.action-button.primary {
  background: var(--primary);
  border-color: var(--primary);
  color: #fff;
}

.action-button:hover,
.action-button:focus-visible,
.dpad-button:hover,
.dpad-button:focus-visible {
  border-color: var(--primary);
  color: var(--primary);
}

.action-button.primary:hover,
.action-button.primary:focus-visible {
  color: #fff;
  opacity: 0.92;
}

.side-panel {
  display: grid;
  gap: 16px;
}

.score-card,
.meta-card,
.help-box {
  border: 1px solid var(--line);
  border-radius: 18px;
  background: #fbfcfc;
}

.score-card {
  padding: 18px;
  background: var(--primary-soft);
  border-color: #bfe5de;
}

.score-card span,
.meta-card span {
  display: block;
  margin-bottom: 8px;
  color: var(--muted);
  font-size: 0.88rem;
}

.score-card strong,
.meta-card strong {
  display: block;
  font-size: clamp(1.4rem, 4vw, 2rem);
  line-height: 1.1;
}

.meta-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
}

.meta-card,
.help-box {
  padding: 16px;
}

.help-box ul {
  margin: 0;
  padding-left: 18px;
}

.dpad {
  display: grid;
  gap: 10px;
  justify-items: center;
}

.dpad-middle {
  display: flex;
  gap: 10px;
}

.dpad-button {
  width: 56px;
  height: 56px;
  border-radius: 18px;
  font-size: 1.1rem;
}

@media (max-width: 900px) {
  .layout,
  .meta-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 640px) {
  .page {
    width: min(100% - 14px, 1040px);
    padding: 14px 0 28px;
  }

  .hero,
  .panel {
    padding: 16px;
    border-radius: 18px;
  }

  .panel-heading {
    flex-direction: column;
  }

  .board {
    gap: 2px;
    padding: 10px;
  }

  .action-button,
  .dpad-button {
    font-size: 16px;
  }

  .controls-row {
    display: grid;
    grid-template-columns: 1fr;
  }
}