.game-header {
    margin-bottom: 2rem;
}

.game-info-top {
    display: flex;
    justify-content: space-between;
    align-items: flex-end;
    margin-bottom: 1.5rem;
}

.game-info-top h1 {
    font-size: 2.5rem;
    margin-bottom: 0;
}

.game-stats {
    display: flex;
    gap: 2rem;
}

.stat-item {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-weight: 700;
    font-size: 1.1rem;
    color: var(--text-dim);
}

.stat-item i {
    color: var(--accent-cyan);
    width: 20px;
}

.game-controls-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: rgba(255, 255, 255, 0.05);
    padding: 0.8rem 1.5rem;
    border-radius: 20px;
    border: 1px solid var(--border-glass);
}

.difficulty-selector {
    display: flex;
    gap: 0.5rem;
}

.diff-btn {
    background: transparent;
    border: 1px solid transparent;
    color: var(--text-dim);
    padding: 0.4rem 1.2rem;
    border-radius: 12px;
    cursor: pointer;
    font-weight: 600;
    transition: var(--transition);
}

.diff-btn:hover {
    color: var(--text-white);
}

.diff-btn.active {
    background: rgba(157, 80, 255, 0.2);
    color: var(--accent-purple);
    border-color: var(--accent-purple);
}

.btn-play-small {
    padding: 0.5rem 1.5rem;
    border-radius: 50px;
    background: transparent;
    border: 1.5px solid var(--accent-cyan);
    color: var(--accent-cyan);
    font-weight: 700;
    cursor: pointer;
    transition: var(--transition);
}

.btn-play-small:hover {
    background: var(--accent-cyan);
    color: #000;
}

/* Sudoku Board */
.sudoku-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 2.5rem;
}

.sudoku-board {
    display: grid;
    grid-template-columns: repeat(9, minmax(0, 1fr));
    grid-template-rows: repeat(9, minmax(0, 1fr));
    width: 100%;
    max-width: 540px;
    aspect-ratio: 1 / 1;
    background: var(--bg-card);
    border: 3px solid var(--text-white);
    border-radius: 8px;
    overflow: hidden;
}

.cell {
    width: 100%;
    height: 100%;
    border: 1px solid rgba(255, 255, 255, 0.1);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.8rem;
    font-weight: 700;
    cursor: pointer;
    transition: var(--transition);
    user-select: none;
    position: relative;
}

/* 3x3 Borders */
.cell:nth-child(3n) { border-right: 2px solid var(--text-white); }
.cell:nth-child(9n) { border-right: none; }
.cell:nth-child(n+19):nth-child(-n+27),
.cell:nth-child(n+46):nth-child(-n+54) { border-bottom: 2px solid var(--text-white); }

.cell.original {
    color: var(--text-white);
    background: rgba(255, 255, 255, 0.03);
}

.cell.user-fill {
    color: var(--accent-cyan);
}

.cell:hover {
    background: rgba(255, 255, 255, 0.1);
}

.cell.selected {
    background: rgba(0, 242, 255, 0.2) !important;
    outline: 2px solid var(--accent-cyan);
    z-index: 5;
}

.cell.highlight {
    background: rgba(255, 255, 255, 0.05);
}

.cell.error {
    background: rgba(255, 0, 0, 0.2) !important;
    color: #ff4d4d !important;
}

.notes-container {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    grid-template-rows: repeat(3, 1fr);
    width: 100%;
    height: 100%;
    padding: 2px;
    pointer-events: none;
    position: absolute;
    inset: 0;
}

.note-num {
    font-size: 0.65rem;
    color: var(--text-dim);
    display: flex;
    align-items: center;
    justify-content: center;
    line-height: 1;
}

.btn-ctrl {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 1.2rem;
    border-radius: 50px;
    background: rgba(255, 255, 255, 0.05);
    border: 1.5px solid var(--border-glass);
    color: var(--text-dim);
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
}

.btn-ctrl:hover {
    color: var(--text-white);
    border-color: var(--text-white);
}

.btn-ctrl.active {
    background: var(--accent-cyan);
    color: #000 !important;
    border-color: var(--accent-cyan);
}

/* Number Pad */
.number-pad {
    display: flex;
    gap: 0.8rem;
    width: 100%;
    max-width: 540px;
    justify-content: center;
}

.num-btn {
    flex: 1;
    aspect-ratio: 1 / 1;
    max-width: 50px;
    background: var(--bg-card);
    border: 1px solid var(--border-glass);
    border-radius: 12px;
    color: var(--text-white);
    font-size: 1.4rem;
    font-weight: 700;
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
}

.num-btn:hover {
    border-color: var(--accent-cyan);
    color: var(--accent-cyan);
    transform: translateY(-3px);
}

.num-btn.action {
    background: rgba(255, 255, 255, 0.05);
    color: var(--text-dim);
}

/* Loading Overlay */
.loading-overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(13, 15, 20, 0.9);
    backdrop-filter: blur(5px);
    display: none;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 1.5rem;
    z-index: 50;
    border-radius: 8px;
}

.loading-overlay.active {
    display: flex;
}

.loader {
    width: 48px;
    height: 48px;
    border: 3px solid var(--accent-cyan);
    border-bottom-color: transparent;
    border-radius: 50%;
    display: inline-block;
    box-sizing: border-box;
    animation: rotation 1s linear infinite;
}

@keyframes rotation {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

.loading-overlay p {
    color: var(--accent-cyan);
    font-weight: 700;
    font-size: 1.1rem;
    letter-spacing: 1px;
}

.sudoku-container {
    position: relative;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 2.5rem;
}


.loader-small {
    width: 24px;
    height: 24px;
    border: 2px solid var(--accent-cyan);
    border-bottom-color: transparent;
    border-radius: 50%;
    margin: 2rem auto;
    animation: rotation 1s linear infinite;
}

.diff-tag {
    font-size: 0.7rem;
    padding: 2px 6px;
    border-radius: 4px;
    background: rgba(255, 255, 255, 0.1);
    color: var(--text-dim);
    margin-left: 4px;
}

.rank-avatar {
    display: flex;
    align-items: center;
    justify-content: center;
    color: #fff;
    font-weight: 800;
    font-size: 0.9rem;
    text-shadow: 0 1px 2px rgba(0,0,0,0.3);
}

@media (max-width: 600px) {
    .cell { font-size: 1.2rem; }
    .num-btn { font-size: 1.1rem; }
    .sudoku-board { max-width: 95vw; }
}