:root {
    --square-size: 72px;
    --piece-size: 50px;
    --selected-piece-size: 50px;
}

body {
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    min-height: 100vh;
    margin: 0;
    padding: 8px 0;
    overflow-y: auto;
    background-color: #2c2c2c;
    font-family: sans-serif;
    color: white;
    text-align: center;
}

h2 {
    margin: 4px 0 6px;
}

#game-status {
    margin: 0 0 6px;
    font-size: 18px;
    font-weight: 700;
    color: #d9edff;
}

p {
    margin: 0 0 6px;
}

/* Scrolling wrapper to contain the massive width */
.board-wrapper {
    width: 98%;
    margin: 0 auto;
    overflow-x: auto;
    overflow-y: hidden;
    padding-bottom: 10px;
    /* Custom scrollbar styling for better visibility */
    scrollbar-width: thin;
    scrollbar-color: #b58863 #1a1a1a;
}

/* The 1D Board Container */
.board {
    display: flex;
    flex-direction: row;
    border: 4px solid #1a1a1a;
    box-shadow: 0 10px 20px rgba(0,0,0,0.5);
    background-color: #1a1a1a;
    width: max-content; /* Allows it to grow beyond screen width */
}

/* Individual Squares */
.square {
    width: var(--square-size);
    height: var(--square-size);
    display: flex;
    position: relative;
    justify-content: center;
    align-items: center;
    flex-shrink: 0; /* Prevents squares from squishing */
}

.square.row-break::after {
    content: '';
    position: absolute;
    top: 0;
    right: 0;
    width: 2px;
    height: 100%;
    background: rgba(0, 0, 0, 0.75);
    pointer-events: none;
    z-index: 3;
}

.light { background-color: #f0d9b5; }
.dark { background-color: #b58863; }

.square.drag-over {
    opacity: 0.8;
    box-shadow: inset 0 0 10px rgba(0,0,0,0.5);
}

.piece {
    cursor: pointer;
    user-select: none;
    font-size: var(--piece-size);
    line-height: 1;
    z-index: 2;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
}

.coord-file,
.coord-rank {
    position: absolute;
    font-size: 10px;
    line-height: 1;
    z-index: 1;
    font-weight: 700;
    pointer-events: none;
    opacity: 0.95;
}

.coord-file {
    left: 4px;
    bottom: 3px;
}

.coord-rank {
    right: 4px;
    bottom: 3px;
}

.light .coord-file,
.light .coord-rank {
    color: #9f6f4e;
}

.dark .coord-file,
.dark .coord-rank {
    color: #f7e6ca;
}

body.hide-notations .coord-file,
body.hide-notations .coord-rank,
body.hide-notations .preview-coord-file,
body.hide-notations .preview-coord-rank {
    display: none;
}

.preview-coord-file,
.preview-coord-rank {
    position: absolute;
    font-size: 10px;
    line-height: 1;
    z-index: 1;
    font-weight: 700;
    pointer-events: none;
    opacity: 0.95;
}

.preview-coord-file {
    left: 4px;
    bottom: 3px;
}

.preview-coord-rank {
    left: 4px;
    top: 3px;
}

.preview-square.light .preview-coord-file,
.preview-square.light .preview-coord-rank {
    color: #9f6f4e;
}

.preview-square.dark .preview-coord-file,
.preview-square.dark .preview-coord-rank {
    color: #f7e6ca;
}

.piece.white-piece {
    color: #f4f1e8;
    text-shadow: 1px 1px 0 #1a1a1a, 2px 2px 4px rgba(0,0,0,0.45);
}

.piece.black-piece {
    color: #111111;
    text-shadow: 1px 1px 0 rgba(255,255,255,0.2), 2px 2px 4px rgba(0,0,0,0.4);
}

.piece.selected {
    transform: translateY(-2px);
}

.square.selected-square {
    box-shadow: inset 0 0 0 4px #5cc8ff;
}

.square.legal-move {
    box-shadow: inset 0 0 0 3px rgba(72, 201, 119, 0.95);
}

.square.legal-capture {
    box-shadow: inset 0 0 0 3px rgba(231, 76, 60, 0.95);
}

.square.checked-king {
    box-shadow: inset 0 0 0 4px rgba(255, 70, 70, 0.98);
    animation: king-check-pulse 1.2s ease-in-out infinite;
}

@keyframes king-check-pulse {
    0%, 100% {
        filter: brightness(1);
    }
    50% {
        filter: brightness(1.2);
    }
}

#turn-indicator {
    margin: 4px 0 8px;
    font-weight: 700;
    letter-spacing: 0.3px;
}

#board-loading {
    margin: 0 auto 8px;
    padding: 6px 10px;
    width: fit-content;
    border-radius: 8px;
    border: 1px solid rgba(255,255,255,0.2);
    background: rgba(255,255,255,0.08);
    color: #eaf6ff;
    font-size: 13px;
    font-weight: 700;
    letter-spacing: 0.4px;
}

.settings-panel {
    margin: 10px auto 0;
    width: min(98%, 760px);
    border: 1px solid rgba(255,255,255,0.14);
    border-radius: 12px;
    background: rgba(255,255,255,0.05);
    box-shadow: 0 6px 16px rgba(0,0,0,0.2);
    overflow: hidden;
}

.settings-panel summary {
    cursor: pointer;
    list-style: none;
    padding: 10px 14px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    font-size: 13px;
    letter-spacing: 0.6px;
    text-transform: uppercase;
    font-weight: 700;
    color: #e5edf5;
    background: rgba(255,255,255,0.06);
    user-select: none;
}

.settings-panel summary::-webkit-details-marker {
    display: none;
}

.summary-arrow {
    font-size: 13px;
    opacity: 0.9;
    transform: rotate(0deg);
    transition: transform 0.2s ease;
}

details[open] > summary .summary-arrow {
    transform: rotate(90deg);
}

.settings-content {
    display: flex;
    flex-direction: column;
    gap: 10px;
    padding: 12px 14px;
}

.settings-row {
    display: flex;
    align-items: center;
    gap: 12px;
    flex-wrap: wrap;
}

.settings-row label {
    font-size: 13px;
    letter-spacing: 0.5px;
    text-transform: uppercase;
    font-weight: 700;
    color: #e5edf5;
}

.settings-checks {
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
}

.settings-checks label {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    text-transform: none;
    letter-spacing: 0.2px;
    font-weight: 600;
    font-size: 13px;
    color: #eaf6ff;
}

.settings-checks input[type="checkbox"] {
    width: 16px;
    height: 16px;
    accent-color: #5cc8ff;
}

#size-slider {
    width: 210px;
}

#size-value {
    min-width: 44px;
    text-align: right;
    font-weight: 700;
    color: #d8f0ff;
}

#fen-input {
    flex: 1;
    min-width: 260px;
    padding: 8px 10px;
    border-radius: 8px;
    border: 1px solid rgba(255,255,255,0.2);
    background: rgba(0,0,0,0.2);
    color: #f2f7fb;
    font-size: 14px;
}

#ai-level,
#player-side {
    padding: 8px 10px;
    border-radius: 8px;
    border: 1px solid rgba(255,255,255,0.2);
    background: rgba(0,0,0,0.2);
    color: #f2f7fb;
    font-size: 14px;
}

#apply-fen,
#restart-game,
#fit-to-screen {
    padding: 8px 12px;
    border: 1px solid rgba(255,255,255,0.2);
    border-radius: 8px;
    background: rgba(92,200,255,0.18);
    color: #eaf8ff;
    font-weight: 700;
    cursor: pointer;
}

#apply-fen:hover,
#restart-game:hover,
#fit-to-screen:hover {
    background: rgba(92,200,255,0.28);
}

#fen-status {
    min-height: 18px;
    font-size: 13px;
    text-align: left;
    color: #cfe9ff;
}

#fen-status.error {
    color: #ff9f9f;
}

#ai-status {
    min-height: 18px;
    font-size: 13px;
    text-align: left;
    color: #d9edff;
}

.ai-settings[hidden] {
    display: none;
}

.faq-panel {
    margin: 10px auto 0;
    width: min(98%, 760px);
    border: 1px solid rgba(255,255,255,0.14);
    border-radius: 12px;
    background: rgba(255,255,255,0.05);
    box-shadow: 0 6px 16px rgba(0,0,0,0.2);
    overflow: hidden;
    text-align: left;
}

.faq-item {
    border-top: 1px solid rgba(255,255,255,0.08);
}

.faq-item:first-of-type {
    border-top: none;
}

.faq-item summary {
    cursor: pointer;
    list-style: none;
    padding: 10px 14px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    color: #e9f4ff;
    font-size: 13px;
    font-weight: 700;
    letter-spacing: 0.2px;
    background: rgba(255,255,255,0.03);
}

.faq-item summary::-webkit-details-marker {
    display: none;
}

.faq-answer {
    padding: 10px 14px 12px;
    color: #d9e8f4;
    font-size: 13px;
    line-height: 1.45;
}

.faq-answer a,
.faq-answer a:visited {
    color: #ffffff;
    text-decoration: underline;
}

.promotion-modal {
    position: fixed;
    inset: 0;
    display: none;
    align-items: center;
    justify-content: center;
    background: rgba(0,0,0,0.55);
    z-index: 50;
}

.promotion-modal.open {
    display: flex;
}

.promotion-dialog {
    width: min(92vw, 420px);
    border-radius: 14px;
    padding: 16px;
    background: #24303a;
    border: 1px solid rgba(255,255,255,0.2);
    box-shadow: 0 18px 40px rgba(0,0,0,0.5);
}

.promotion-title {
    margin: 0 0 10px;
    font-size: 16px;
    letter-spacing: 0.4px;
    color: #eaf6ff;
}

.promotion-options {
    display: grid;
    grid-template-columns: repeat(4, minmax(56px, 1fr));
    gap: 8px;
}

.promotion-option {
    height: 64px;
    border-radius: 10px;
    border: 1px solid rgba(255,255,255,0.2);
    background: rgba(255,255,255,0.08);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 38px;
    line-height: 1;
}

.promotion-option:hover {
    background: rgba(92, 200, 255, 0.2);
    border-color: rgba(92, 200, 255, 0.6);
}

.promotion-option .piece {
    cursor: default;
    font-size: 38px;
}

.mode-modal {
    position: fixed;
    inset: 0;
    background: rgba(12, 14, 18, 0.74);
    backdrop-filter: blur(2px) grayscale(0.12);
    display: none;
    align-items: center;
    justify-content: center;
    padding: 16px;
    z-index: 100;
}

.mode-modal.open {
    display: flex;
}

.mode-dialog {
    width: min(92vw, 520px);
    min-height: 220px;
    background: #1f1f1f;
    border: 1px solid rgba(255,255,255,0.18);
    border-radius: 14px;
    box-shadow: 0 18px 38px rgba(0,0,0,0.45);
    padding: 22px 22px;
    text-align: center;
    display: flex;
    flex-direction: column;
    justify-content: center;
}

.mode-title {
    margin: 0;
    font-size: 22px;
    color: #eef8ff;
}

.mode-description {
    margin: 10px 0 0;
    color: #d6e6f5;
    line-height: 1.45;
    font-size: 14px;
}

.mode-actions {
    margin-top: 14px;
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    justify-content: center;
}

.mode-button {
    border: 1px solid rgba(255,255,255,0.22);
    border-radius: 8px;
    padding: 9px 12px;
    color: #f0f7fd;
    font-weight: 700;
    cursor: pointer;
    background: rgba(255,255,255,0.08);
}

.mode-button:hover {
    background: rgba(255,255,255,0.14);
}

.mode-button.primary {
    background: rgba(92,200,255,0.28);
    border-color: rgba(92,200,255,0.55);
}

.mode-button.primary:hover {
    background: rgba(92,200,255,0.4);
}

#selected-piece-indicator {
    margin: 10px auto 0;
    min-height: 64px;
    width: fit-content;
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 10px 14px;
    border: 1px solid rgba(255,255,255,0.18);
    border-radius: 14px;
    background: linear-gradient(145deg, rgba(255,255,255,0.08), rgba(255,255,255,0.03));
    box-shadow: 0 8px 18px rgba(0,0,0,0.25);
    color: #eef3f8;
}

#selected-piece-indicator .label {
    font-size: 12px;
    letter-spacing: 1.1px;
    text-transform: uppercase;
    opacity: 0.85;
    font-weight: 700;
}

#selected-piece-indicator .piece-slot {
    width: 56px;
    height: 56px;
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 10px;
    background: rgba(0,0,0,0.22);
    border: 1px solid rgba(255,255,255,0.14);
}

#selected-piece-indicator .piece-slot.empty {
    font-size: 12px;
    letter-spacing: 0.5px;
    text-transform: uppercase;
    color: rgba(238,243,248,0.75);
}

#selected-piece-indicator .meta {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    gap: 3px;
}

#selected-piece-indicator .notation-label {
    font-size: 11px;
    text-transform: uppercase;
    letter-spacing: 0.9px;
    opacity: 0.75;
}

#selected-piece-indicator .notation-value {
    font-size: 16px;
    font-weight: 700;
    letter-spacing: 0.5px;
    color: #ffffff;
}

#selected-piece-indicator .piece {
    font-size: var(--selected-piece-size);
    line-height: 1;
    vertical-align: middle;
    cursor: default;
    margin-left: 0;
}

.preview-wrapper {
    width: min(98%, 420px);
    margin: 8px auto 0;
    display: none;
}

.preview-wrapper.visible {
    display: block;
}

.preview-title {
    margin: 0 0 8px;
    font-size: 12px;
    letter-spacing: 1px;
    text-transform: uppercase;
    opacity: 0.85;
}

.preview-board {
    display: grid;
    grid-template-columns: repeat(8, 1fr);
    border: 3px solid #1a1a1a;
    box-shadow: 0 8px 16px rgba(0,0,0,0.35);
    background: #1a1a1a;
    pointer-events: none;
    user-select: none;
}

.preview-square {
    aspect-ratio: 1;
    display: flex;
    position: relative;
    align-items: center;
    justify-content: center;
    font-size: 34px;
}

.preview-piece {
    font-size: 34px;
    line-height: 1;
}

@media (max-width: 640px) {
    .settings-checks {
        flex-direction: column;
        align-items: flex-start;
        gap: 10px;
    }

    .settings-checks label {
        width: 100%;
        justify-content: flex-start;
    }

    .ai-controls-row {
        display: grid;
        grid-template-columns: minmax(84px, auto) minmax(0, 1fr);
        gap: 10px 12px;
        align-items: center;
    }

    .ai-controls-row label {
        justify-self: start;
    }

    .ai-controls-row select {
        width: 100%;
        min-width: 0;
    }
}