body {
    margin: 0;
    font-family: Arial, sans-serif;
    background: #f5f7fa;
}

/* 🔝 Navbar */
.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: #1e293b;
    color: white;
    padding: 15px 30px;
}

.navbar a {
    color: white;
    margin-left: 15px;
    text-decoration: none;
}

.navbar a:hover {
    text-decoration: underline;
}

/* 📦 Layout */
.container {
    max-width: 900px;
    margin: 30px auto;
    padding: 10px;
}

/* 📇 Cards */
.card {
    background: white;
    padding: 20px;
    margin-bottom: 25px;
    border-radius: 12px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
}

.game-card {
    text-align: center;
}

#statusMessage {
    min-height: 24px;
    margin: 0 0 8px;
    font-weight: bold;
}

.board {
    overflow-x: auto;
    padding-bottom: 8px;
}

/* ♟️ Board */
.board-grid {
    --label-size: 30px;
    --cell-size: 60px;
    display: grid;
    grid-template-columns: var(--label-size) repeat(var(--board-size, 8), var(--cell-size));
    grid-template-rows: var(--label-size) repeat(var(--board-size, 8), var(--cell-size));
    margin: 20px auto;
    width: max-content;
    border: 6px solid #1e293b;
    border-radius: 10px;
    overflow: hidden;
    max-width: 100%;
}

.label {
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    background: #aec8eb;
    color: #1e293b;
    width: var(--label-size);
    height: var(--label-size);
    font-size: 14px;
}

.cell {
    width: var(--cell-size);
    height: var(--cell-size);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: calc(var(--cell-size) * 0.5);
    cursor: pointer;
    transition: 0.2s;
}

.cell:hover {
    transform: scale(1.05);
}

.cell.solver-place {
    box-shadow: inset 0 0 0 4px #22c55e;
    animation: solverPulse 0.35s ease;
}

.cell.solver-remove {
    box-shadow: inset 0 0 0 4px #f59e0b;
    animation: solverPulse 0.35s ease;
}

.cell.solver-solution {
    box-shadow: inset 0 0 0 4px #2563eb;
    animation: solverPulse 0.35s ease;
}

.white {
    background: #e2e8f0;
}

.black {
    background: #475569;
    color: white;
}

.invalid {
    background: #ef4444 !important;
}

/* 🎛️ Buttons */
.controls {
    margin-top: 15px;
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 10px;
}

.btn {
    padding: 10px 15px;
    margin: 5px;
    border: none;
    border-radius: 8px;
    background: #3b82f6;
    color: white;
    cursor: pointer;
}

.btn:hover {
    background: #2563eb;
}

.btn:disabled,
.btn:disabled:hover {
    background: #94a3b8;
    cursor: not-allowed;
}

.btn.secondary {
    background: #64748b;
}

.btn.secondary:hover {
    background: #475569;
}

.btn.danger {
    background: #ef4444;
}

.btn.danger:hover {
    background: #dc2626;
}

#queenList {
    list-style: none;
    padding: 0;
}

#queenList li {
    padding: 5px;
    background: #f1f5f9;
    margin: 4px 0;
    border-radius: 6px;
}

.mode-switch {
    margin-bottom: 15px;
}

.mode-switch .btn {
    margin: 5px;
}

.btn.active {
    background: #22c55e;
}

.solver-panel {
    margin-top: 12px;
    padding: 16px;
    border-radius: 12px;
    border: 1px solid #dbe4ee;
    background: #f8fafc;
    text-align: left;
}

.solver-panel-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: 16px;
}

.solver-panel h3 {
    margin: 0 0 6px;
    color: #1e293b;
}

.solver-message {
    margin: 0;
    color: #475569;
}

.solver-step-info {
    margin: 0;
    padding: 6px 10px;
    border-radius: 999px;
    background: #dbeafe;
    color: #1d4ed8;
    font-size: 14px;
    font-weight: bold;
    white-space: nowrap;
}

.solver-controls {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-top: 14px;
}

.solver-controls .btn,
.controls .btn {
    margin: 0;
}

.solver-speed {
    display: grid;
    grid-template-columns: auto 1fr auto;
    align-items: center;
    gap: 12px;
    margin-top: 14px;
}

.solver-speed input[type="range"] {
    width: 100%;
}

.solver-speed-label {
    font-weight: bold;
    color: #334155;
}

.solver-speed-value {
    min-width: 62px;
    text-align: right;
    color: #475569;
    font-variant-numeric: tabular-nums;
}

.board-size-info {
    margin: 0 0 10px;
    color: #475569;
}

.sidebar {
    position: fixed;
    top: 0;
    right: 0;
    width: min(320px, 85vw);
    height: 100vh;
    padding: 24px;
    box-sizing: border-box;
    background: white;
    box-shadow: -10px 0 24px rgba(15, 23, 42, 0.18);
    transform: translateX(100%);
    transition: transform 0.25s ease;
    overflow-y: auto;
    -webkit-overflow-scrolling: touch;
    overscroll-behavior: contain;
    z-index: 30;
}

.sidebar.open {
    transform: translateX(0);
}

.save-points-sidebar {
    width: min(380px, 92vw);
}

.save-sidebar {
    width: min(360px, 90vw);
}

.sidebar-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 10px;
}

.sidebar-close {
    margin: 0;
}

.sidebar-label {
    display: block;
    margin-top: 18px;
    margin-bottom: 8px;
    font-weight: bold;
}

.sidebar input[type="range"] {
    width: 100%;
}

.sidebar-input {
    width: 100%;
    padding: 10px 12px;
    border: 1px solid #cbd5e1;
    border-radius: 8px;
    font: inherit;
    box-sizing: border-box;
    background: #fff;
}

.sidebar-textarea {
    resize: vertical;
    min-height: 96px;
}

.sidebar-checkbox {
    display: flex;
    align-items: center;
    gap: 10px;
    margin: 16px 0 18px;
    color: #334155;
}

.sidebar-size-row {
    margin: 12px 0 18px;
    font-size: 18px;
}

.sidebar-hint {
    color: #64748b;
    font-size: 14px;
}

.save-points-list {
    display: grid;
    gap: 12px;
    margin-top: 18px;
}

.save-point-filters {
    display: grid;
    gap: 8px;
    margin-top: 18px;
    padding-bottom: 16px;
    border-bottom: 1px solid #e2e8f0;
}

.save-point-card {
    border: 1px solid #dbe4ee;
    border-radius: 10px;
    padding: 14px;
    background: #f8fafc;
}

.save-point-card h4 {
    margin: 0 0 8px;
    color: #1e293b;
}

.save-point-meta {
    margin: 4px 0;
    color: #475569;
    font-size: 14px;
}

.save-point-preview {
    margin: 10px 0 0;
    color: #334155;
    font-size: 14px;
    word-break: break-word;
}

.save-point-note {
    margin: 10px 0 0;
    color: #475569;
    font-size: 14px;
}

.save-point-actions {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-top: 14px;
}

.save-point-actions .btn {
    margin: 0;
}

.btn.ghost {
    background: #e2e8f0;
    color: #1e293b;
}

.btn.ghost:hover {
    background: #cbd5e1;
}

.sidebar-backdrop {
    position: fixed;
    inset: 0;
    background: rgba(15, 23, 42, 0.3);
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.25s ease;
    z-index: 20;
}

.sidebar-backdrop.visible {
    opacity: 1;
    pointer-events: auto;
}

@keyframes solverPulse {
    0% {
        transform: scale(0.97);
    }

    50% {
        transform: scale(1.03);
    }

    100% {
        transform: scale(1);
    }
}

@media (max-width: 720px) {
    .container {
        padding: 12px;
    }

    .navbar {
        padding: 15px 18px;
    }

    .solver-panel-header,
    .solver-speed {
        grid-template-columns: 1fr;
        display: grid;
    }

    .solver-step-info,
    .solver-speed-value {
        justify-self: start;
    }
}