:root {
  --board-bg: #eef1f5;
  --line-color: #b8c0cc;
  --meta-line-color: #333a44;
  --circle-color: #3d5afe;
  --cross-color: #e0553f;
  --accent: #3d5afe;
  --accent2: #7c4dff;
  --grad: linear-gradient(120deg, var(--accent), var(--accent2));
  --btn-c1: var(--accent);
  --btn-c2: var(--accent2);
  --btn-grad: linear-gradient(120deg, var(--btn-c1), var(--btn-c2));
  --bg: #f4f1ea;
  --text: #2b2b2b;
  --card-bg: #ffffff;
  --card-border: #e6e2d8;
  --muted: #6b6b66;
  --hero-grid: rgba(20, 20, 40, 0.05);
  --active-bg: #fff4d6;
  --black-win-bg: #c3cfff;
  --white-win-bg: #ffceba;
  --draw-bg: #d5d5d5;
}

:root[data-theme="dark"] {
  --board-bg: #2a2d33;
  --line-color: #4a5262;
  --meta-line-color: #6b7280;
  --circle-color: #7c93ff;
  --cross-color: #ff7a63;
  --accent: #7c93ff;
  --accent2: #a78bfa;
  /* ボタンの塗りは文字用のaccentよりトーンを落として、暗い背景で発光しすぎないようにする */
  --btn-c1: #3d5afe;
  --btn-c2: #7c4dff;
  --bg: #121214;
  --text: #ececee;
  --card-bg: #1c1c20;
  --card-border: #2c2c31;
  --muted: #9a9aa2;
  --hero-grid: rgba(255, 255, 255, 0.06);
  --active-bg: #4a3f1f;
  --black-win-bg: #2d3563;
  --white-win-bg: #5c3624;
  --draw-bg: #3a3a3a;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Hiragino Sans", "Yu Gothic", "Meiryo", sans-serif;
  background-color: var(--bg);
  background-image:
    radial-gradient(circle, var(--hero-grid) 1px, transparent 1px),
    radial-gradient(900px circle at 15% -10%, color-mix(in srgb, var(--accent) 12%, transparent), transparent 55%),
    radial-gradient(800px circle at 100% 10%, color-mix(in srgb, var(--accent2) 9%, transparent), transparent 55%);
  background-size: 22px 22px, auto, auto;
  background-attachment: fixed;
  color: var(--text);
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  align-items: center;
}

.site-header {
  text-align: center;
  padding: 1.2rem 1rem 0.4rem;
}

.site-header h1 {
  margin: 0;
  font-size: 1.8rem;
  font-weight: 800;
  letter-spacing: -0.01em;
  background: var(--grad);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.subtitle {
  margin: 0.3rem 0 0;
  color: var(--muted);
  font-size: 0.95rem;
}

.ad-slot {
  width: 100%;
  max-width: 640px;
  min-height: 60px;
  margin: 0.8rem auto;
  display: flex;
  align-items: center;
  justify-content: center;
  background: repeating-linear-gradient(45deg, #eee, #eee 10px, #e2e2e2 10px, #e2e2e2 20px);
  color: #999;
  font-size: 0.8rem;
  border-radius: 6px;
}

:root[data-theme="dark"] .ad-slot {
  background: repeating-linear-gradient(45deg, #1c1c20, #1c1c20 10px, #232328 10px, #232328 20px);
  color: #9a9aa2;
}

main {
  width: 100%;
  max-width: 640px;
  padding: 0 1rem 2rem;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.hidden {
  display: none !important;
}

.game-area {
  width: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.setup-screen {
  width: 100%;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: 12px;
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.06);
  padding: 1.5rem 1.2rem;
  margin-bottom: 1rem;
  text-align: center;
}

.setup-screen h2 {
  margin-top: 0;
  font-size: 1.15rem;
}

.mode-buttons {
  display: flex;
  flex-direction: column;
  gap: 0.7rem;
  max-width: 320px;
  margin: 1rem auto 0;
}

.mode-btn {
  padding: 0.8rem 1rem;
  border: none;
  border-radius: 8px;
  background: var(--btn-grad);
  color: #fff;
  font-size: 1rem;
  font-weight: bold;
  cursor: pointer;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}

.mode-btn:hover {
  transform: translateY(-1px);
  box-shadow: 0 6px 16px color-mix(in srgb, var(--btn-c1) 35%, transparent);
}

.mode-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

.link-btn {
  border: none;
  background: none;
  color: var(--accent);
  font-size: 0.85rem;
  cursor: pointer;
  text-decoration: underline;
  padding: 0.3rem;
}

.online-choice {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
  margin-top: 1rem;
}

.join-row {
  display: flex;
  gap: 0.5rem;
  align-items: center;
  justify-content: center;
  flex-wrap: wrap;
}

.join-row input {
  padding: 0.6rem 0.7rem;
  border: 1px solid var(--card-border);
  border-radius: 6px;
  background: var(--card-bg);
  color: var(--text);
  font-size: 1rem;
  width: 130px;
  text-align: center;
  text-transform: uppercase;
  letter-spacing: 0.15em;
}

.host-wait {
  margin-top: 1.2rem;
  padding-top: 1rem;
  border-top: 1px solid var(--card-border);
}

.room-code {
  font-size: 2rem;
  font-weight: bold;
  letter-spacing: 0.2em;
  color: var(--accent);
  margin: 0.5rem 0;
}

.online-status {
  color: var(--muted);
  font-size: 0.9rem;
  margin: 0.5rem 0 0;
}

.online-error {
  color: #c0392b;
  font-size: 0.9rem;
  margin-top: 0.8rem;
}

#online-connection-status {
  width: 100%;
  text-align: center;
  margin: 0 0 0.6rem;
}

#quit-online-btn {
  margin-top: 0.8rem;
}

.status-bar {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 0.6rem;
}

.turn-indicator {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: bold;
}

.stone-preview {
  width: 22px;
  height: 22px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
  font-weight: 800;
  line-height: 1;
}

.stone-preview.black::before {
  content: "○";
  color: var(--circle-color);
}

.stone-preview.white::before {
  content: "×";
  color: var(--cross-color);
}

.reset-btn {
  padding: 0.5rem 1rem;
  border: none;
  border-radius: 6px;
  background: var(--btn-grad);
  color: #fff;
  font-size: 0.9rem;
  cursor: pointer;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}

.reset-btn:hover {
  transform: translateY(-1px);
  box-shadow: 0 6px 16px color-mix(in srgb, var(--btn-c1) 35%, transparent);
}

.forced-hint {
  width: 100%;
  text-align: center;
  margin: 0 0 0.6rem;
  font-size: 0.85rem;
  color: var(--muted);
}

.board-wrapper {
  width: 100%;
  display: flex;
  justify-content: center;
}

.meta-board {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  gap: 6px;
  background: var(--meta-line-color);
  border: 4px solid var(--meta-line-color);
  border-radius: 6px;
  width: 100%;
  max-width: 480px;
  aspect-ratio: 1 / 1;
  touch-action: manipulation;
}

.meta-board.thinking {
  pointer-events: none;
  opacity: 0.7;
}

.sub-board {
  position: relative;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  background: var(--board-bg);
  transition: background 0.15s ease;
}

.sub-board.active {
  background: var(--active-bg);
  box-shadow: inset 0 0 0 3px var(--accent);
}

.sub-board.decided .mini-cell {
  pointer-events: none;
}

.sub-board.won-black {
  background: var(--black-win-bg);
  box-shadow: inset 0 0 0 3px var(--circle-color);
}

.sub-board.won-white {
  background: var(--white-win-bg);
  box-shadow: inset 0 0 0 3px var(--cross-color);
}

.sub-board.drawn {
  background: var(--draw-bg);
}

.sub-board.decided .mini-cell::after {
  opacity: 0;
}

.mini-cell {
  position: relative;
  border-right: 1px solid var(--line-color);
  border-bottom: 1px solid var(--line-color);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
}

.mini-cell::after {
  content: "";
  font-size: clamp(1rem, 6vw, 1.9rem);
  font-weight: 800;
  line-height: 1;
  transform: scale(0);
  transition: transform 0.12s ease-out;
}

.mini-cell.black::after {
  content: "○";
  color: var(--circle-color);
  transform: scale(1);
}

.mini-cell.white::after {
  content: "×";
  color: var(--cross-color);
  transform: scale(1);
}

.sub-winner-mark {
  position: absolute;
  inset: 0;
  display: none;
  align-items: center;
  justify-content: center;
  font-size: clamp(2.2rem, 13vw, 3.2rem);
  font-weight: 800;
  pointer-events: none;
  text-shadow:
    0 0 6px rgba(255, 255, 255, 0.95),
    0 0 12px rgba(255, 255, 255, 0.95),
    0 1px 2px rgba(0, 0, 0, 0.25);
}

.sub-board.decided .sub-winner-mark {
  display: flex;
}

.sub-winner-mark.black {
  color: var(--circle-color);
}

.sub-winner-mark.white {
  color: var(--cross-color);
}

.sub-winner-mark.draw {
  color: #777;
  font-size: 1.6rem;
  text-shadow:
    0 0 6px rgba(255, 255, 255, 0.95),
    0 0 12px rgba(255, 255, 255, 0.95);
}

.overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.55);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
}

.overlay.hidden {
  display: none;
}

.overlay-card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: 12px;
  padding: 1.5rem 2rem;
  text-align: center;
  max-width: 90%;
  width: 360px;
  position: relative;
  z-index: 1001;
}

.result-text {
  font-size: 1.4rem;
  font-weight: bold;
  margin: 0 0 1rem;
}

.other-games {
  margin-top: 1.2rem;
  border-top: 1px solid var(--card-border);
  padding-top: 1rem;
}

.other-games p {
  margin: 0 0 0.5rem;
  font-weight: bold;
  color: var(--muted);
}

.other-games ul {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  justify-content: center;
}

.other-games a {
  display: inline-block;
  padding: 0.4rem 0.8rem;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: 999px;
  color: var(--accent);
  text-decoration: none;
  font-size: 0.85rem;
  transition: border-color 0.15s ease, transform 0.15s ease;
}

.other-games a:hover {
  border-color: var(--accent);
  transform: translateY(-1px);
}

.howto {
  width: 100%;
  margin-top: 2rem;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  padding: 1rem 1.2rem;
  border-radius: 8px;
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.06);
}

.howto h2 {
  margin-top: 0;
  font-size: 1.2rem;
}

.howto ul {
  padding-left: 1.2rem;
  line-height: 1.6;
}

.site-footer {
  margin-top: auto;
  padding: 1rem;
  color: var(--muted);
  font-size: 0.8rem;
}

@media (max-width: 480px) {
  .site-header h1 {
    font-size: 1.4rem;
  }
  .overlay-card {
    padding: 1.2rem 1rem;
  }
}

.site-nav {
  width: 100%;
  padding: 0.6rem 1rem;
  font-size: 0.85rem;
  box-sizing: border-box;
}
.site-nav a {
  display: inline-flex;
  align-items: center;
  color: var(--text);
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: 999px;
  padding: 0.35rem 0.9rem;
  text-decoration: none;
  transition: border-color 0.15s ease, transform 0.15s ease;
}
.site-nav a:hover {
  border-color: var(--accent);
  transform: translateY(-1px);
}