/* ========== CSS VARIABLES & THEMES ========== */
:root {
    --bg: #0a0e17;
    --bg2: #111827;
    --surface: #1a1f2e;
    --surface2: #1e2435;
    --text: #e2e8f0;
    --text2: #a0aec0;
    --text3: #718096;
    --accent: #4da6ff;
    --accent2: #3b82f6;
    --gold: #f0c060;
    --gold2: #d4a030;
    --danger: #ef4444;
    --danger2: #dc2626;
    --success: #22c55e;
    --border: #2d3548;
    --border2: #3d4558;
    --shadow: 0 4px 24px rgba(0, 0, 0, 0.4);
    --shadow2: 0 2px 8px rgba(0, 0, 0, 0.3);
    --radius: 16px;
    --radius2: 10px;
    --radius3: 8px;
    --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
    --font: 'Inter', 'Segoe UI', system-ui, -apple-system, sans-serif;
    --board-light: #f0d9b5;
    --board-dark: #b58863;
    --board-light-hover: #e8cfa0;
    --board-dark-hover: #a0754a;
    --board-selected: rgba(255, 215, 0, 0.55);
    --board-legal: rgba(0, 0, 0, 0.18);
    --board-capture: rgba(255, 60, 60, 0.5);
    --board-lastmove: rgba(255, 215, 0, 0.35);
    --board-check: rgba(255, 30, 30, 0.6);
    --glass-bg: rgba(26, 31, 46, 0.75);
    --glass-border: rgba(255, 255, 255, 0.08);
    --glass-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
    --timer-pulse: #ef4444;
}

[data-theme="light"] {
    --bg: #f1f5f9;
    --bg2: #e2e8f0;
    --surface: #ffffff;
    --surface2: #f8fafc;
    --text: #1a202c;
    --text2: #4a5568;
    --text3: #a0aec0;
    --border: #e2e8f0;
    --border2: #cbd5e0;
    --shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
    --shadow2: 0 2px 6px rgba(0, 0, 0, 0.05);
    --glass-bg: rgba(255, 255, 255, 0.8);
    --glass-border: rgba(0, 0, 0, 0.06);
    --glass-shadow: 0 4px 16px rgba(0, 0, 0, 0.06);
    --board-light: #f0d9b5;
    --board-dark: #b58863;
    --board-light-hover: #e8cfa0;
    --board-dark-hover: #a0754a;
}

/* Board Themes */
[data-board-theme="classic"] {
    --board-light: #f0d9b5;
    --board-dark: #b58863;
    --board-light-hover: #e8cfa0;
    --board-dark-hover: #a0754a;
}
[data-board-theme="emerald"] {
    --board-light: #e0f0e0;
    --board-dark: #5a8a6a;
    --board-light-hover: #c8e8c8;
    --board-dark-hover: #4a7a5a;
}
[data-board-theme="midnight"] {
    --board-light: #d0d8e8;
    --board-dark: #2c3e6b;
    --board-light-hover: #bcc8e0;
    --board-dark-hover: #1e3055;
}
[data-board-theme="rose"] {
    --board-light: #f8e8e0;
    --board-dark: #c0887a;
    --board-light-hover: #f0d8d0;
    --board-dark-hover: #a87060;
}
[data-board-theme="bw"] {
    --board-light: #e8e8e8;
    --board-dark: #555555;
    --board-light-hover: #d8d8d8;
    --board-dark-hover: #444444;
}
[data-board-theme="neon"] {
    --board-light: #1a1a2e;
    --board-dark: #0f0f1a;
    --board-light-hover: #222240;
    --board-dark-hover: #1a1a30;
}

/* ========== RESET & BASE ========== */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
    -webkit-tap-highlight-color: transparent;
}

body {
    font-family: var(--font);
    background: var(--bg);
    background-image: radial-gradient(ellipse at 30% 20%, rgba(30, 50, 80, 0.35) 0%, transparent 60%),
        radial-gradient(ellipse at 70% 60%, rgba(20, 30, 50, 0.3) 0%, transparent 55%);
    color: var(--text);
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 16px;
    transition: background var(--transition), color var(--transition);
    user-select: none;
    -webkit-user-select: none;
    overflow-x: hidden;
}

button {
    cursor: pointer;
    font-family: inherit;
}

svg {
    fill: currentColor;
}

/* Helper Utility Classes */
.text-center { text-align: center; }
.text-bold { font-weight: 700; font-size: 1rem; }
.text-sub { font-size: 0.75rem; color: var(--text3); margin-top: 4px; }
.flex-gap-4 { display: flex; gap: 4px; }
.max-w-500 { max-width: 500px !important; }

/* ========== MAIN CONTAINER ========== */
.app-container {
    display: flex;
    gap: 24px;
    max-width: 1200px;
    width: 100%;
    align-items: flex-start;
    justify-content: center;
    flex-wrap: wrap;
}

/* ========== BOARD SECTION ========== */
.board-section {
    flex: 0 0 auto;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 12px;
}

.board-wrapper {
    background: var(--surface);
    border-radius: var(--radius);
    padding: 12px;
    box-shadow: var(--shadow);
    border: 1px solid var(--border);
    position: relative;
    transition: all var(--transition);
}

.board-container {
    display: grid;
    grid-template-columns: repeat(8, 1fr);
    grid-template-rows: repeat(8, 1fr);
    width: min(85vw, 560px);
    height: min(85vw, 560px);
    position: relative;
    border-radius: var(--radius3);
    overflow: hidden;
    box-shadow: var(--shadow2);
    touch-action: manipulation;
}

.square {
    position: relative;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background-color 0.12s ease;
    aspect-ratio: 1;
    font-size: clamp(10px, 1.8vw, 13px);
    font-weight: 600;
    color: var(--text3);
    z-index: 1;
}

.square.light {
    background-color: var(--board-light);
    color: var(--board-dark);
}

.square.dark {
    background-color: var(--board-dark);
    color: var(--board-light);
}

.square.light:hover { background-color: var(--board-light-hover); }
.square.dark:hover { background-color: var(--board-dark-hover); }

.square.selected {
    box-shadow: inset 0 0 0 4px var(--board-selected);
    z-index: 3;
}

.square.last-move {
    box-shadow: inset 0 0 0 3px var(--board-lastmove);
}

.square.in-check {
    animation: checkGlow 0.6s ease-in-out infinite alternate;
    box-shadow: inset 0 0 0 4px var(--board-check);
    z-index: 4;
}

.square.legal-move::after {
    content: '';
    position: absolute;
    width: 28%;
    height: 28%;
    background: var(--board-legal);
    border-radius: 50%;
    pointer-events: none;
    z-index: 2;
    transition: all 0.1s;
}

.square.capture-move::after {
    content: '';
    position: absolute;
    width: 88%;
    height: 88%;
    border-radius: 50%;
    border: 5px solid var(--board-capture);
    pointer-events: none;
    z-index: 2;
    box-sizing: border-box;
}

.square.drag-over {
    box-shadow: inset 0 0 0 4px rgba(100, 180, 255, 0.7);
    z-index: 5;
}

.coord-label {
    position: absolute;
    font-size: 11px;
    font-weight: 700;
    pointer-events: none;
    z-index: 2;
    opacity: 0.8;
    letter-spacing: 0.5px;
}

.coord-file { bottom: 3px; right: 5px; }
.coord-rank { top: 3px; left: 5px; }

@keyframes checkGlow {
    0% { box-shadow: inset 0 0 0 4px var(--board-check); }
    100% { box-shadow: inset 0 0 0 8px rgba(255, 30, 30, 0.85), 0 0 20px rgba(255, 30, 30, 0.4); }
}

.piece-img {
    width: 82%;
    height: 82%;
    object-fit: contain;
    pointer-events: none;
    z-index: 2;
    filter: drop-shadow(1px 2px 2px rgba(0, 0, 0, 0.25));
    transition: transform 0.1s ease;
    position: relative;
}

.piece-img.dragging {
    opacity: 0.5;
    transform: scale(1.1);
}

.piece-img.animating {
    transition: transform 0.22s cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

/* Board controls */
.board-controls {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
    justify-content: center;
}

.btn {
    padding: 9px 16px;
    border-radius: var(--radius3);
    border: 1px solid var(--border);
    background: var(--surface);
    color: var(--text);
    font-size: 0.85rem;
    font-weight: 500;
    transition: all var(--transition);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    white-space: nowrap;
    letter-spacing: 0.01em;
}

.btn svg {
    width: 18px;
    height: 18px;
    flex: 0 0 auto;
    display: block;
}

.btn:hover {
    background: var(--surface2);
    border-color: var(--border2);
    transform: translateY(-1px);
}

.btn:hover svg, .btn:focus-visible svg {
    transform: translateY(-0.5px);
    transition: transform 0.15s ease;
}

.btn:active {
    transform: scale(0.97);
    transition: transform 0.08s;
}

.btn.accent {
    background: var(--accent);
    color: #fff;
    border-color: var(--accent);
    font-weight: 600;
}

.btn.accent:hover {
    background: var(--accent2);
    box-shadow: 0 4px 14px rgba(59, 130, 246, 0.35);
}

.btn.danger {
    background: transparent;
    color: var(--danger);
    border-color: var(--danger);
}

.btn.danger:hover {
    background: var(--danger);
    color: #fff;
}

.btn.small {
    padding: 6px 10px;
    font-size: 0.75rem;
    border-radius: 6px;
}

.btn.small svg {
    width: 16px;
    height: 16px;
}

.btn.icon-btn {
    width: 44px;
    height: 44px;
    padding: 0;
}

.btn.icon-btn svg {
    width: 20px;
    height: 20px;
}

/* ========== SIDE PANEL ========== */
.side-panel {
    flex: 1 1 320px;
    max-width: 400px;
    min-width: 280px;
    display: flex;
    flex-direction: column;
    gap: 14px;
}

.panel-card {
    background: var(--glass-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius);
    padding: 16px;
    box-shadow: var(--glass-shadow);
    transition: all var(--transition);
}

.panel-actions {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
    justify-content: center;
}

.player-header {
    display: flex;
    align-items: center;
    gap: 12px;
}

.player-avatar {
    width: 42px;
    height: 42px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 1rem;
    flex-shrink: 0;
}

.player-avatar.white {
    background: #f8f8f8;
    color: #333;
    border: 2px solid #ddd;
}

.player-avatar.black {
    background: #1a1a1a;
    color: #e0e0e0;
    border: 2px solid #444;
}

.player-info {
    flex: 1;
    min-width: 0;
}

.player-name {
    font-weight: 600;
    font-size: 0.95rem;
    letter-spacing: 0.01em;
}

.player-status {
    font-size: 0.75rem;
    color: var(--text2);
    margin-top: 2px;
}

.player-status.active {
    color: var(--accent);
    font-weight: 600;
}

.player-status.check-status {
    color: var(--danger);
    font-weight: 700;
    animation: pulse 1s ease-in-out infinite;
}

.player-timer {
    font-size: 1.5rem;
    font-weight: 700;
    font-variant-numeric: tabular-nums;
    font-family: 'SF Mono', 'JetBrains Mono', 'Consolas', monospace;
    letter-spacing: 0.03em;
    transition: color 0.3s;
}

.player-timer.low-time {
    color: var(--timer-pulse);
    animation: pulse 0.5s ease-in-out infinite;
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.5; }
}

.captured-row {
    display: flex;
    flex-wrap: wrap;
    gap: 2px;
    min-height: 28px;
    align-items: center;
    padding: 4px 0;
}

.captured-piece {
    width: 22px;
    height: 22px;
    object-fit: contain;
    opacity: 0.85;
}

.history-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 8px;
}

.move-history {
    max-height: 180px;
    overflow-y: auto;
    font-size: 0.8rem;
    font-family: 'SF Mono', 'JetBrains Mono', 'Consolas', monospace;
    line-height: 1.7;
    padding-right: 4px;
    scroll-behavior: smooth;
}

.move-history::-webkit-scrollbar { width: 4px; }
.move-history::-webkit-scrollbar-thumb {
    background: var(--border2);
    border-radius: 4px;
}

.move-row {
    display: flex;
    gap: 8px;
    padding: 2px 6px;
    border-radius: 4px;
    cursor: pointer;
    transition: background 0.15s;
}

.move-row:hover { background: var(--surface); }
.move-row.current {
    background: var(--accent);
    color: #fff;
    font-weight: 600;
}

.move-number {
    color: var(--text3);
    min-width: 28px;
    font-weight: 600;
}

.move-row.current .move-number { color: #fff; }
.move-white, .move-black { min-width: 50px; }

/* ========== MODALS ========== */
.modal-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.65);
    z-index: 100;
    display: flex;
    align-items: center;
    justify-content: center;
    animation: fadeIn 0.2s ease;
    backdrop-filter: blur(3px);
    -webkit-backdrop-filter: blur(3px);
}

.modal-overlay.hidden { display: none; }

.modal {
    background: var(--surface);
    border-radius: var(--radius);
    padding: 28px 24px;
    max-width: 440px;
    width: 90%;
    box-shadow: 0 20px 50px rgba(0, 0, 0, 0.5);
    animation: scaleIn 0.25s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    text-align: center;
    border: 1px solid var(--border);
}

.modal h2 {
    font-size: 1.3rem;
    margin-bottom: 12px;
    letter-spacing: 0.02em;
}

.modal p {
    color: var(--text2);
    font-size: 0.9rem;
    margin-bottom: 18px;
    line-height: 1.5;
}

.modal-buttons {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    justify-content: center;
}

.promotion-options {
    display: flex;
    gap: 14px;
    justify-content: center;
    flex-wrap: wrap;
}

.promotion-btn {
    width: 64px;
    height: 64px;
    border-radius: var(--radius3);
    cursor: pointer;
    border: 3px solid var(--border);
    background: var(--surface2);
    transition: all var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 6px;
}

.promotion-btn:hover {
    border-color: var(--accent);
    transform: scale(1.08);
    box-shadow: 0 6px 20px rgba(59, 130, 246, 0.3);
}

.promotion-btn img {
    width: 100%;
    height: 100%;
    object-fit: contain;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes scaleIn {
    from { transform: scale(0.85); opacity: 0; }
    to { transform: scale(1); opacity: 1; }
}

/* ========== TOAST ========== */
.toast-container {
    position: fixed;
    bottom: 24px;
    left: 50%;
    transform: translateX(-50%);
    z-index: 200;
    display: flex;
    flex-direction: column;
    gap: 8px;
    pointer-events: none;
}

.toast {
    background: var(--surface);
    color: var(--text);
    padding: 12px 20px;
    border-radius: 30px;
    font-size: 0.85rem;
    font-weight: 500;
    box-shadow: var(--shadow);
    border: 1px solid var(--border);
    animation: toastIn 0.35s ease, toastOut 0.3s ease 2.2s forwards;
    pointer-events: auto;
    text-align: center;
    letter-spacing: 0.01em;
}

.toast.error {
    border-color: var(--danger);
    color: var(--danger);
}

.toast.success {
    border-color: var(--success);
    color: var(--success);
}

@keyframes toastIn {
    from { transform: translateY(30px); opacity: 0; }
    to { transform: translateY(0); opacity: 1; }
}

@keyframes toastOut {
    from { opacity: 1; }
    to { opacity: 0; transform: translateY(-10px); }
}

/* ========== SETTINGS MODAL ========== */
.settings-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 10px;
    text-align: left;
    margin-bottom: 16px;
}

.settings-grid label {
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--text2);
    letter-spacing: 0.02em;
    display: flex;
    align-items: center;
}

.settings-grid select,
.settings-grid input {
    width: 100%;
    padding: 8px 10px;
    border-radius: 6px;
    border: 1px solid var(--border);
    background: var(--surface2);
    color: var(--text);
    font-family: var(--font);
    font-size: 0.85rem;
}

/* ========== RESPONSIVE ========== */
@media (max-width: 900px) {
    .app-container {
        flex-direction: column;
        align-items: center;
        gap: 16px;
    }
    .side-panel {
        max-width: 560px;
        width: 100%;
        flex: auto;
    }
    .board-container {
        width: min(92vw, 500px);
        height: min(92vw, 500px);
    }
    .modal {
        max-width: 95vw;
        padding: 20px 16px;
    }
    .settings-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 400px) {
    .board-container {
        width: 94vw;
        height: 94vw;
    }
    .btn {
        padding: 7px 10px;
        font-size: 0.75rem;
    }
    .player-timer {
        font-size: 1.2rem;
    }
    .side-panel {
        min-width: auto;
    }
}

@media (prefers-reduced-motion: reduce) {
    *, *::before, *::after {
        animation-duration: 0.01ms !important;
        transition-duration: 0.01ms !important;
    }
}