:root {
    --bg-color: #f8fafc;
    --surface-color: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --primary-color: #3b82f6;
    --primary-hover: #2563eb;
    --cell-empty: #e2e8f0;
    --cell-empty-hover: #cbd5e1;
    --cell-fixed: #f1f5f9;
    --cell-fixed-text: #334155;
    --cell-filled: #eff6ff;
    --cell-filled-text: #1d4ed8;
    --cell-border: #cbd5e1;
    --operator-color: #94a3b8;
    --result-color: #0f172a;
    --bank-bg: #ffffff;
    --bank-shadow: 0 -4px 6px -1px rgba(0, 0, 0, 0.05);
    --success-color: #10b981;
    --error-color: #ef4444;
}

[data-theme="dark"] {
    --bg-color: #0f172a;
    --surface-color: #1e293b;
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --primary-color: #3b82f6;
    --primary-hover: #60a5fa;
    --cell-empty: #334155;
    --cell-empty-hover: #475569;
    --cell-fixed: #1e293b;
    --cell-fixed-text: #cbd5e1;
    --cell-filled: #1e3a8a;
    --cell-filled-text: #bfdbfe;
    --cell-border: #475569;
    --operator-color: #64748b;
    --result-color: #f1f5f9;
    --bank-bg: #1e293b;
    --bank-shadow: 0 -4px 6px -1px rgba(0, 0, 0, 0.3);
}

body {
    background-color: var(--bg-color);
    color: var(--text-primary);
    transition: background-color 0.3s ease, color 0.3s ease;
    margin: 0;
    font-family: 'Outfit', sans-serif;
}

#game-ui {
    max-width: 600px;
    margin: 0 auto 60px auto;
    position: relative;
    display: flex;
    flex-direction: column;
    min-height: 80vh;
}

#top-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem;
    background: var(--surface-color);
    border-radius: 1rem;
    margin-bottom: 1rem;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.05);
}

.hud-item {
    display: flex;
    flex-direction: column;
}

.hud-label {
    font-size: 0.75rem;
    font-weight: 700;
    color: var(--text-secondary);
    letter-spacing: 0.05em;
}

.hud-value {
    font-size: 1.5rem;
    font-weight: 900;
    color: var(--text-primary);
}

.hud-controls {
    display: flex;
    gap: 0.5rem;
}

.icon-btn {
    background: var(--cell-empty);
    border: none;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    font-size: 1.25rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: transform 0.2s, background 0.2s;
}

.icon-btn:hover {
    transform: scale(1.05);
    background: var(--cell-empty-hover);
}

#board-container {
    flex-grow: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 1rem;
}

#crossmath-board {
    display: grid;
    gap: 4px;
    background: var(--surface-color);
    padding: 12px;
    border-radius: 12px;
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

.board-cell {
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.25rem;
    font-weight: 700;
    border-radius: 8px;
    user-select: none;
}

@media (min-width: 400px) {
    .board-cell {
        width: 50px;
        height: 50px;
        font-size: 1.5rem;
    }
}

.cell-empty {
    background: var(--cell-empty);
    cursor: pointer;
    transition: background 0.2s, transform 0.1s;
    border: 2px dashed var(--cell-border);
}
.cell-empty.highlight {
    background: var(--cell-empty-hover);
    border-color: var(--primary-color);
}
.cell-empty.selected {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 4px rgba(59, 130, 246, 0.2);
}

.cell-filled {
    background: var(--cell-filled);
    color: var(--cell-filled-text);
    cursor: pointer;
    border: 2px solid var(--primary-color);
    animation: popIn 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

.cell-fixed {
    background: var(--cell-fixed);
    color: var(--cell-fixed-text);
    border: 2px solid var(--cell-border);
}

.cell-op, .cell-eq {
    color: var(--operator-color);
    font-weight: 900;
    font-size: 1.5rem;
}

.cell-res {
    color: var(--result-color);
    font-weight: 900;
}

.cell-none {
    background: transparent;
}

#bank-container {
    background: var(--bank-bg);
    padding: 1rem;
    border-radius: 1rem 1rem 0 0;
    box-shadow: var(--bank-shadow);
    margin-top: auto;
}

#number-bank {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    justify-content: center;
}

.bank-number {
    width: 50px;
    height: 50px;
    background: var(--primary-color);
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    font-weight: 700;
    border-radius: 12px;
    cursor: pointer;
    box-shadow: 0 4px 6px -1px rgba(59, 130, 246, 0.5);
    transition: transform 0.2s, box-shadow 0.2s;
    user-select: none;
}

.bank-number:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 8px -1px rgba(59, 130, 246, 0.6);
}

.bank-number:active {
    transform: translateY(0);
}

.bank-number.used {
    opacity: 0.3;
    pointer-events: none;
    transform: scale(0.9);
    box-shadow: none;
}

.bank-number.selected {
    box-shadow: 0 0 0 4px rgba(59, 130, 246, 0.4);
    transform: scale(1.1);
}

@keyframes popIn {
    0% { transform: scale(0.5); opacity: 0; }
    100% { transform: scale(1); opacity: 1; }
}

.overlay {
    position: absolute;
    top: 0; left: 0; width: 100%; height: 100%;
    background: rgba(15, 23, 42, 0.8);
    backdrop-filter: blur(4px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 100;
    border-radius: 1rem;
}

.overlay.hidden {
    display: none;
}

.overlay-inner {
    background: var(--surface-color);
    padding: 2rem;
    border-radius: 1.5rem;
    text-align: center;
    box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.2);
    animation: slideUp 0.4s ease-out;
}

.lc-stars {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

@keyframes slideUp {
    0% { transform: translateY(20px); opacity: 0; }
    100% { transform: translateY(0); opacity: 1; }
}

.primary-btn {
    background: var(--primary-color);
    color: white;
    border: none;
    padding: 1rem 2rem;
    border-radius: 999px;
    font-size: 1.125rem;
    font-weight: 700;
    cursor: pointer;
    margin-top: 1.5rem;
    transition: background 0.2s, transform 0.2s;
}

.primary-btn:hover {
    background: var(--primary-hover);
    transform: translateY(-2px);
}

#feedback-message {
    position: absolute;
    top: 50%; left: 50%;
    transform: translate(-50%, -50%);
    background: rgba(0,0,0,0.8);
    color: white;
    padding: 1rem 2rem;
    border-radius: 2rem;
    font-size: 1.25rem;
    font-weight: 700;
    z-index: 50;
    pointer-events: none;
    opacity: 0;
    transition: opacity 0.3s;
}
#feedback-message.show {
    opacity: 1;
    animation: floatUp 1s ease-out;
}
@keyframes floatUp {
    0% { transform: translate(-50%, -40%); opacity: 1; }
    100% { transform: translate(-50%, -80%); opacity: 0; }
}

.wrong-anim {
    animation: shake 0.4s cubic-bezier(.36,.07,.19,.97) both;
    border-color: var(--error-color) !important;
    background: rgba(239, 68, 68, 0.1) !important;
    color: var(--error-color) !important;
}

@keyframes shake {
    10%, 90% { transform: translate3d(-1px, 0, 0); }
    20%, 80% { transform: translate3d(2px, 0, 0); }
    30%, 50%, 70% { transform: translate3d(-4px, 0, 0); }
    40%, 60% { transform: translate3d(4px, 0, 0); }
}

.correct-anim {
    border-color: var(--success-color) !important;
    color: var(--success-color) !important;
}

.game-description {
    text-align: center;
    padding: 1rem;
    max-width: 800px;
    margin: 0 auto;
}