body, html {
    margin: 0;
    padding: 0;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: #3a3a3a;
    background-image: linear-gradient(45deg, #2b2b2b 25%, transparent 25%, transparent 75%, #2b2b2b 75%, #2b2b2b),
                      linear-gradient(-45deg, #2b2b2b 25%, transparent 25%, transparent 75%, #2b2b2b 75%, #2b2b2b);
    background-size: 60px 60px;
    color: #e0e0e0;
    min-height: 100vh;
    box-sizing: border-box;
    overflow-x: hidden;
}

.game-container {
    display: flex;
    flex-direction: row;
    align-items: flex-start;
    justify-content: center;
    gap: 30px;
    padding: 15px;
    width: 100%;
    box-sizing: border-box;
    flex-wrap: wrap;
}

#board {
    width: 90vmin;
    height: 90vmin;
    max-width: 720px;
    max-height: 720px;
    aspect-ratio: 1 / 1;
    display: grid;
    grid-template-columns: repeat(8, 1fr);
    grid-template-rows: repeat(8, 1fr);
    background-image: url('assets/board.png');
    background-size: cover;
    border: 6px solid #6f5f4f;
    border-radius: 4px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.5);
    flex-shrink: 0;
}

.side-panel {
    display: flex;
    flex-direction: column;
    gap: 20px;
    width: 240px;
    flex-shrink: 0;
}

.square {
    display: flex;
    justify-content: center;
    align-items: center;
    box-sizing: border-box;
    position: relative;
    user-select: none;
    background-size: 90%;
    background-repeat: no-repeat;
    background-position: center;
}
.square:hover { cursor: pointer; }

.wp { background-image: url('assets/wp.png'); }
.wn { background-image: url('assets/wn.png'); }
.wb { background-image: url('assets/wb.png'); }
.wr { background-image: url('assets/wr.png'); }
.wq { background-image: url('assets/wq.png'); }
.wk { background-image: url('assets/wk.png'); }
.bp { background-image: url('assets/bp.png'); }
.bn { background-image: url('assets/bn.png'); }
.bb { background-image: url('assets/bb.png'); }
.br { background-image: url('assets/br.png'); }
.bq { background-image: url('assets/bq.png'); }
.bk { background-image: url('assets/bk.png'); }

.highlight-selected::after, .highlight-valid::after, .highlight-last::after, .highlight-check::after {
    content: '';
    position: absolute;
    top: 0; left: 0;
    width: 100%; height: 100%;
    box-sizing: border-box;
    pointer-events: none;
    z-index: 1;
    border-radius: 2px;
}
.highlight-selected::after { border: 4px solid rgba(255, 255, 0, 0.7); }
.highlight-valid::after { content: ''; position: absolute; top: 50%; left: 50%; width: 20%; height: 20%; min-width: 8px; min-height: 8px; background-color: rgba(0, 0, 0, 0.35); border-radius: 50%; transform: translate(-50%, -50%); border: 1px solid rgba(255, 255, 255, 0.2); }
.highlight-last::after { background-color: rgba(50, 150, 255, 0.3); }
.highlight-check::after { background-color: rgba(255, 50, 50, 0.45); }

#info-panel, #controls-panel {
    width: 100%;
    padding: 15px;
    background-color: #4a4a4a;
    border-radius: 8px;
    box-shadow: 0 3px 10px rgba(0,0,0,0.4);
    color: #f0f0f0;
    font-size: 1em;
    line-height: 1.5;
    box-sizing: border-box;
}

#controls-panel {
    display: flex;
    flex-direction: column;
    gap: 10px;
    align-items: center;
}

#depth-selector {
    width: 70px;
    padding: 5px;
    background-color: #333;
    color: #fff;
    border: 1px solid #666;
    border-radius: 4px;
}

#start-game-btn {
    width: 100%;
    padding: 8px;
    background-color: #007bff;
    color: #fff;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    transition: background-color 0.2s ease;
}
#start-game-btn:hover { background-color: #0056b3; }

#promotion-choice { position: absolute; background-color: rgba(70, 70, 70, 0.95); border: 1px solid #aaa; padding: 5px; z-index: 10; display: none; gap: 5px; border-radius: 4px; box-shadow: 0 2px 8px rgba(0,0,0,0.5); }
.promotion-button { width: 60px; height: 60px; cursor: pointer; border: 1px solid #666; background-color: #ccc; background-size: 90%; background-repeat: no-repeat; background-position: center; border-radius: 3px; transition: background-color 0.2s ease, border-color 0.2s ease; }
.promotion-button:hover { background-color: #e0e0e0; border-color: #fff; }

@media (max-width: 1000px) {
    body, html { display: block; padding: 15px 0; }
    .game-container { flex-direction: column; align-items: center; gap: 20px; padding: 10px; }
    .side-panel { width: 90vmin; max-width: 720px; }
    #info-panel, #controls-panel { text-align: center; }
    .promotion-button { width: 50px; height: 50px; }
}

@media (max-width: 400px) {
    #info-panel, #controls-panel { font-size: 0.9em; }
    .promotion-button { width: 40px; height: 40px; }
}