:root {
    --bg: #f5f1e8;
    --board: #dbb576;
    --board-border: #5c3a1e;
    --black: #1a1a1a;
    --white: #f2f2f2;
    --accent: #8c4a1f;
    --text: #2c241b;
    --nav-bg: #2b2520;
    --nav-text: #f5f1e8;
    --card-bg: #ffffff;
    --shadow: rgba(0, 0, 0, 0.08);
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.5;
}

.site-nav {
    background: var(--nav-bg);
    color: var(--nav-text);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0.5rem 1rem;
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.25);
    flex-wrap: wrap;
    gap: 0.5rem;
}

.site-nav a {
    color: var(--nav-text);
    text-decoration: none;
    padding: 0.45rem 0.75rem;
    border-radius: 0.35rem;
    font-weight: 500;
    opacity: 0.8;
    transition: background 0.15s, opacity 0.15s;
}

.site-nav a:hover {
    opacity: 1;
    background: rgba(255, 255, 255, 0.08);
}

.site-nav a.active {
    opacity: 1;
    background: var(--accent);
}

.site-nav .logo {
    font-size: 1.2rem;
    font-weight: 700;
    opacity: 1;
}

.nav-links {
    display: flex;
    gap: 0.1rem;
    flex-wrap: wrap;
}

main {
    max-width: 820px;
    margin: 0 auto;
    padding: 1rem 0.75rem 2rem;
}

.tab-content {
    display: none;
    animation: fade-in 0.2s ease-out;
}

.tab-content.active {
    display: block;
}

@keyframes fade-in {
    from {
        opacity: 0;
        transform: translateY(4px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.card {
    background: var(--card-bg);
    border-radius: 0.5rem;
    box-shadow: 0 2px 8px var(--shadow);
    padding: 1.25rem;
    margin-bottom: 1rem;
}

.card h2 {
    margin-top: 0;
    color: var(--accent);
}

.controls,
.actions {
    display: flex;
    flex-wrap: wrap;
    gap: 0.6rem;
    justify-content: center;
    align-items: flex-end;
    margin-bottom: 0.8rem;
}

.controls label {
    display: flex;
    flex-direction: column;
    font-size: 0.8rem;
    font-weight: 600;
    min-width: 4.5rem;
}

.controls select,
.actions button,
.controls button {
    padding: 0.45rem 0.7rem;
    border-radius: 0.35rem;
    border: 1px solid #bda07d;
    background: #fff;
    color: var(--text);
    font-size: 0.95rem;
    cursor: pointer;
    touch-action: manipulation;
}

.actions button,
.controls button.primary {
    border: 1px solid var(--accent);
    background: var(--accent);
    color: #fff;
    min-width: 5rem;
    font-weight: 600;
}

.actions button.secondary,
.controls button.secondary {
    background: #fff;
    color: var(--accent);
}

button:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.status {
    text-align: center;
    font-weight: 700;
    min-height: 1.6rem;
    margin-bottom: 0.4rem;
    font-size: 1.05rem;
}

.board-wrap {
    display: flex;
    justify-content: center;
    margin: 0.4rem 0 1rem;
}

#board {
    width: min(95vw, 600px);
    height: auto;
    background: var(--board);
    border: 2px solid var(--board-border);
    border-radius: 0.4rem;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
    touch-action: none;
    user-select: none;
}

#board line {
    stroke: var(--board-border);
    stroke-width: 0.35;
}

#board .stone {
    stroke-width: 0.15;
}

#board .star {
    fill: var(--board-border);
}

#board .last-marker {
    fill: none;
    stroke-width: 0.25;
}

#board .last-marker.black {
    stroke: var(--white);
}

#board .last-marker.white {
    stroke: var(--black);
}

.hidden {
    display: none;
}

@media (max-width: 640px) {
    .site-nav {
        flex-direction: column;
        align-items: stretch;
    }

    .nav-links {
        justify-content: center;
    }

    main {
        padding: 0.75rem 0.5rem 1.5rem;
    }

    .card {
        padding: 1rem;
    }

    .controls label {
        min-width: 5.5rem;
    }
}