:root {
    --green-dark: #155b2c;
    --green-light: #1f7a3d;
    --grid-line: rgba(0, 0, 0, 0.35);
    --highlight: rgba(255, 255, 0, 0.35);
    --bg: #101418;
    --panel-bg: rgba(255, 255, 255, 0.08);
    --text: #f4f7f8;
    --accent: #ffc145;
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: "Segoe UI", "Helvetica Neue", Arial, sans-serif;
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.page-header,
.page-footer {
    text-align: center;
    padding: 1.5rem 1rem;
}

.page-header {
    background: rgba(255, 255, 255, 0.04);
    border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}

.page-header h1 {
    margin: 0;
    font-size: clamp(1.8rem, 2vw + 1rem, 3rem);
}

.page-footer {
    margin-top: auto;
    font-size: 0.85rem;
    color: rgba(255, 255, 255, 0.6);
}

.layout {
    display: flex;
    flex-wrap: wrap;
    gap: 2rem;
    justify-content: center;
    padding: 2rem 1rem 3rem;
}

.board-section {
    flex: 1 1 320px;
    display: flex;
    justify-content: center;
    align-items: center; /* 垂直方向も中央寄せにして Safari で上寄せになるのを防ぐ */
}

/* Wrapper that keeps the board square using the padding-top trick.
   This is more robust across mobile browsers (including older Safari) than
   relying only on aspect-ratio. */
.board-wrapper {
    width: min(90vw, 520px);
    max-width: 520px;
    /* maintain 1:1 ratio */
    position: relative;
    margin: 0 auto; /* 明示的に中央寄せ */
}
.board-wrapper::before {
    content: "";
    display: block;
    padding-top: 100%;
}

.board {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    display: grid;
    grid-template-columns: repeat(8, minmax(0, 1fr));
    background: var(--green-light);
    border: 6px solid #0f3019;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.45);
}

.cell {
    position: relative;
    background: var(--green-dark);
    border: 1px solid var(--grid-line);
    cursor: pointer;
    transition: transform 0.1s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 0;
    outline: none;
    color: transparent;
}

/* Ensure grid cells size properly and are big enough for touch targets */
.board {
    grid-auto-rows: 1fr;
}
.cell {
    min-width: 0;
    min-height: 0;
}

.cell:focus-visible {
    outline: 3px solid var(--accent);
    outline-offset: -1px;
}

.cell:hover {
    transform: scale(1.03);
}

.cell.disabled,
.board.disabled .cell {
    cursor: not-allowed;
    opacity: 0.6;
    transform: none;
}

.cell::after {
    content: "";
    width: 70%;
    height: 70%;
    border-radius: 50%;
    box-shadow: inset 0 6px 12px rgba(0, 0, 0, 0.4);
    transform: scale(0);
    transition: transform 0.15s ease, background 0.15s ease;
}

.cell.black::after {
    background: radial-gradient(circle at 30% 30%, #4a4a4a, #050505 70%);
    transform: scale(1);
}

.cell.white::after {
    background: radial-gradient(circle at 30% 30%, #ffffff, #c6c6c6 70%);
    transform: scale(1);
}

.cell.valid::before {
    content: "";
    position: absolute;
    width: 35%;
    height: 35%;
    border-radius: 50%;
    background: var(--highlight);
    box-shadow: 0 0 10px rgba(255, 255, 0, 0.4);
}

.side-panel {
    flex: 0 1 260px;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    padding: 1.5rem;
    background: var(--panel-bg);
    border-radius: 1rem;
    border: 1px solid rgba(255, 255, 255, 0.08);
    box-shadow: 0 15px 30px rgba(0, 0, 0, 0.3);
    backdrop-filter: blur(6px);
}

.controls {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.controls select,
.controls button {
    font-size: 1rem;
    padding: 0.65rem 0.75rem;
    border-radius: 0.75rem;
    border: none;
}

.controls select {
    background: rgba(0, 0, 0, 0.25);
    color: var(--text);
}

.controls button {
    background: var(--accent);
    color: #1c1c1c;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.1s ease, box-shadow 0.1s ease;
}

.controls button:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 16px rgba(0, 0, 0, 0.25);
}

.controls button:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
    box-shadow: none;
}

.scores {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 1rem;
    text-align: center;
    font-size: 1.1rem;
}

.scores .label {
    display: block;
    font-size: 0.85rem;
    opacity: 0.75;
}

.scores .value {
    font-size: 1.6rem;
    font-weight: 700;
}

.status {
    min-height: 3rem;
    padding: 1rem;
    border-radius: 0.75rem;
    background: rgba(0, 0, 0, 0.25);
    line-height: 1.4;
}

.notes {
    font-size: 0.85rem;
    color: rgba(255, 255, 255, 0.65);
}

.notes code {
    background: rgba(0, 0, 0, 0.45);
    padding: 0.15rem 0.35rem;
    border-radius: 0.4rem;
}

@media (max-width: 768px) {
    .side-panel {
        flex: 1 1 100%;
    }
    .layout {
        gap: 1.5rem;
    }
}