/* ==========================================
   SUDOKU GAME - E-Studios Inspired Design
   ========================================== */

/* CSS Variables */
:root {
    /* Dark Theme Colors */
    --bg-primary: #0d1117;
    --bg-secondary: #161b22;
    --bg-tertiary: #21262d;
    --bg-elevated: #30363d;

    /* Accent Colors */
    --accent-primary: #58a6ff;
    --accent-secondary: #79c0ff;
    --accent-glow: rgba(88, 166, 255, 0.3);
    --accent-success: #3fb950;
    --accent-error: #f85149;
    --accent-warning: #d29922;

    /* Text Colors */
    --text-primary: #f0f6fc;
    --text-secondary: #8b949e;
    --text-muted: #6e7681;

    /* Board Colors */
    --cell-bg: #21262d;
    --cell-bg-hover: #30363d;
    --cell-bg-selected: rgba(88, 166, 255, 0.15);
    --cell-bg-highlighted: rgba(88, 166, 255, 0.08);
    --cell-bg-same-number: rgba(88, 166, 255, 0.2);
    --cell-bg-error: rgba(248, 81, 73, 0.2);
    --cell-border: #30363d;
    --cell-border-thick: #58a6ff;

    /* Shadows */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.5);
    --shadow-glow: 0 0 20px var(--accent-glow);

    /* Transitions */
    --transition-fast: 0.15s ease;
    --transition-normal: 0.25s ease;
    --transition-slow: 0.4s ease;

    /* Spacing */
    --gap-xs: 4px;
    --gap-sm: 8px;
    --gap-md: 16px;
    --gap-lg: 24px;
    --gap-xl: 32px;

    /* Border Radius */
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    --radius-xl: 24px;
}

/* Reset & Base Styles */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
    line-height: 1.5;
    overflow-x: hidden;
}

/* Background Animation */
body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background:
        radial-gradient(ellipse at 20% 20%, rgba(88, 166, 255, 0.08) 0%, transparent 50%),
        radial-gradient(ellipse at 80% 80%, rgba(121, 192, 255, 0.06) 0%, transparent 50%),
        radial-gradient(ellipse at 50% 50%, rgba(88, 166, 255, 0.03) 0%, transparent 70%);
    pointer-events: none;
    z-index: 0;
}

/* App Container */
.app-container {
    position: relative;
    z-index: 1;
    max-width: 500px;
    margin: 0 auto;
    padding: var(--gap-md);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* ==========================================
   HEADER
   ========================================== */
.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--gap-md) 0;
    margin-bottom: var(--gap-lg);
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--gap-sm);
}

.logo-icon {
    width: 42px;
    height: 42px;
    background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: 'Armata', sans-serif;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--bg-primary);
    box-shadow: var(--shadow-glow);
}

.logo-text {
    font-family: 'Armata', sans-serif;
    font-size: 1.5rem;
    letter-spacing: 3px;
    color: var(--text-primary);
}

.header-controls {
    display: flex;
    align-items: center;
    gap: var(--gap-sm);
}

.lang-toggle {
    background: var(--bg-tertiary);
    border: 1px solid var(--cell-border);
    border-radius: var(--radius-md);
    padding: var(--gap-sm) var(--gap-md);
    color: var(--text-primary);
    font-family: 'Armata', sans-serif;
    font-size: 0.875rem;
    letter-spacing: 1px;
    cursor: pointer;
    transition: all var(--transition-normal);
    display: flex;
    align-items: center;
    gap: var(--gap-xs);
}

.lang-toggle:hover {
    background: var(--bg-elevated);
    border-color: var(--accent-primary);
    box-shadow: var(--shadow-glow);
}

.lang-flag {
    font-weight: 600;
}

/* ==========================================
   STATS BAR
   ========================================== */
.stats-bar {
    display: flex;
    justify-content: space-between;
    background: var(--bg-secondary);
    border: 1px solid var(--cell-border);
    border-radius: var(--radius-lg);
    padding: var(--gap-md) var(--gap-lg);
    margin-bottom: var(--gap-lg);
    box-shadow: var(--shadow-md);
}

.stat-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--gap-xs);
}

.stat-label {
    font-size: 0.75rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 1px;
}

.stat-value {
    font-family: 'Armata', sans-serif;
    font-size: 1.125rem;
    color: var(--text-primary);
    font-weight: 600;
}

/* ==========================================
   GAME BOARD
   ========================================== */
.board-wrapper {
    position: relative;
    margin-bottom: var(--gap-lg);
}

.sudoku-board {
    display: grid;
    grid-template-columns: repeat(9, 1fr);
    gap: 1px;
    background: var(--cell-border);
    border: 3px solid var(--accent-primary);
    border-radius: var(--radius-md);
    overflow: hidden;
    box-shadow: var(--shadow-lg), var(--shadow-glow);
    aspect-ratio: 1;
}

.cell {
    background: var(--cell-bg);
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: 'Armata', sans-serif;
    font-size: 1.5rem;
    color: var(--text-primary);
    cursor: pointer;
    transition: all var(--transition-fast);
    position: relative;
    user-select: none;
}

/* 3x3 Box Borders */
.cell:nth-child(3n) {
    border-right: 2px solid var(--accent-primary);
}

.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(--accent-primary);
}

/* Cell States */
.cell:hover:not(.fixed):not(.selected) {
    background: var(--cell-bg-hover);
}

.cell.selected {
    background: var(--cell-bg-selected);
    box-shadow: inset 0 0 0 2px var(--accent-primary);
}

.cell.highlighted {
    background: var(--cell-bg-highlighted);
}

.cell.same-number {
    background: var(--cell-bg-same-number);
}

.cell.fixed {
    color: var(--text-secondary);
    cursor: default;
}

.cell.user-input {
    color: var(--accent-primary);
}

.cell.error {
    background: var(--cell-bg-error);
    color: var(--accent-error);
    animation: shake 0.4s ease;
}

.cell.correct-animation {
    animation: correct-pop 0.3s ease;
}

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    20%, 60% { transform: translateX(-3px); }
    40%, 80% { transform: translateX(3px); }
}

@keyframes correct-pop {
    0% { transform: scale(1); }
    50% { transform: scale(1.15); }
    100% { transform: scale(1); }
}

/* Notes in Cell */
.cell .notes {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    grid-template-rows: repeat(3, 1fr);
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    padding: 2px;
}

.cell .note {
    font-size: 0.55rem;
    color: var(--text-muted);
    display: flex;
    align-items: center;
    justify-content: center;
}

/* ==========================================
   WIN & GAME OVER OVERLAYS
   ========================================== */
.win-overlay,
.gameover-overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(13, 17, 23, 0.95);
    backdrop-filter: blur(8px);
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-normal);
    border-radius: var(--radius-md);
    z-index: 10;
}

.win-overlay.active,
.gameover-overlay.active {
    opacity: 1;
    visibility: visible;
}

.win-content,
.gameover-content {
    text-align: center;
    transform: scale(0.9);
    transition: transform var(--transition-normal);
}

.win-overlay.active .win-content,
.gameover-overlay.active .gameover-content {
    transform: scale(1);
}

.win-icon,
.gameover-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto var(--gap-md);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
}

.win-icon {
    background: linear-gradient(135deg, var(--accent-success), #2ea043);
    box-shadow: 0 0 30px rgba(63, 185, 80, 0.4);
    position: relative;
}

.gameover-icon {
    background: linear-gradient(135deg, var(--accent-error), #da3633);
    box-shadow: 0 0 30px rgba(248, 81, 73, 0.4);
}

.win-icon svg,
.gameover-icon svg {
    width: 40px;
    height: 40px;
    color: white;
}

.win-content h2,
.gameover-content h2 {
    font-family: 'Armata', sans-serif;
    font-size: 1.75rem;
    margin-bottom: var(--gap-sm);
    letter-spacing: 1px;
}

.win-content p,
.gameover-content p {
    color: var(--text-secondary);
    margin-bottom: var(--gap-lg);
}

.win-stats {
    display: flex;
    justify-content: center;
    gap: var(--gap-xl);
    margin-bottom: var(--gap-lg);
}

.win-stat {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.win-stat-label {
    font-size: 0.75rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 1px;
}

.win-stat-value {
    font-family: 'Armata', sans-serif;
    font-size: 1.5rem;
    color: var(--accent-success);
}

/* ==========================================
   NUMBER PAD
   ========================================== */
.number-pad {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: var(--gap-sm);
    margin-bottom: var(--gap-lg);
}

.num-btn {
    background: var(--bg-secondary);
    border: 1px solid var(--cell-border);
    border-radius: var(--radius-md);
    padding: var(--gap-md);
    font-family: 'Armata', sans-serif;
    font-size: 1.25rem;
    color: var(--text-primary);
    cursor: pointer;
    transition: all var(--transition-fast);
    display: flex;
    align-items: center;
    justify-content: center;
}

.num-btn:hover {
    background: var(--bg-elevated);
    border-color: var(--accent-primary);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.num-btn:active {
    transform: translateY(0);
}

.num-btn.disabled {
    opacity: 0.3;
    cursor: not-allowed;
    background: var(--accent-success);
    border-color: var(--accent-success);
    color: var(--bg-primary);
}

.num-btn.disabled:hover {
    transform: none;
    background: var(--accent-success);
    border-color: var(--accent-success);
}

.erase-btn {
    grid-column: span 1;
}

.erase-btn svg {
    width: 24px;
    height: 24px;
}

/* ==========================================
   ACTION BUTTONS
   ========================================== */
.action-buttons {
    display: flex;
    justify-content: center;
    gap: var(--gap-md);
    margin-bottom: var(--gap-lg);
}

.action-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--gap-xs);
    background: var(--bg-secondary);
    border: 1px solid var(--cell-border);
    border-radius: var(--radius-md);
    padding: var(--gap-md) var(--gap-lg);
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-normal);
    position: relative;
    min-width: 80px;
}

.action-btn svg {
    width: 24px;
    height: 24px;
}

.action-btn span {
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.action-btn:hover {
    background: var(--bg-elevated);
    color: var(--text-primary);
    border-color: var(--accent-primary);
}

.action-btn.active {
    background: var(--cell-bg-selected);
    color: var(--accent-primary);
    border-color: var(--accent-primary);
}

.hint-count {
    position: absolute;
    top: -6px;
    right: -6px;
    background: var(--accent-primary);
    color: var(--bg-primary);
    font-size: 0.7rem;
    font-weight: 700;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
}

/* ==========================================
   GAME CONTROLS
   ========================================== */
.game-controls {
    display: flex;
    flex-direction: column;
    gap: var(--gap-md);
    margin-bottom: var(--gap-lg);
}

.difficulty-selector {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--gap-sm);
}

.difficulty-selector label {
    font-size: 0.875rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 1px;
}

.difficulty-buttons {
    display: flex;
    gap: var(--gap-sm);
}

.diff-btn {
    background: var(--bg-tertiary);
    border: 1px solid var(--cell-border);
    border-radius: var(--radius-sm);
    padding: var(--gap-sm) var(--gap-md);
    font-size: 0.875rem;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.diff-btn:hover {
    background: var(--bg-elevated);
    color: var(--text-primary);
}

.diff-btn.active {
    background: var(--accent-primary);
    color: var(--bg-primary);
    border-color: var(--accent-primary);
    font-weight: 600;
}

/* Primary Button */
.btn {
    border: none;
    border-radius: var(--radius-md);
    padding: var(--gap-md) var(--gap-xl);
    font-family: 'Armata', sans-serif;
    font-size: 1rem;
    letter-spacing: 1px;
    cursor: pointer;
    transition: all var(--transition-normal);
}

.btn-primary {
    background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
    color: var(--bg-primary);
    box-shadow: var(--shadow-glow);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 0 30px var(--accent-glow);
}

.btn-primary:active {
    transform: translateY(0);
}

.new-game-btn {
    width: 100%;
}

/* ==========================================
   FOOTER
   ========================================== */
.footer {
    margin-top: auto;
    text-align: center;
    padding: var(--gap-lg) 0;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--gap-md);
}

.footer p {
    font-size: 0.75rem;
    color: var(--text-muted);
}

.footer-brand {
    font-size: 0.8rem;
    color: var(--text-muted);
    display: flex;
    align-items: center;
    gap: var(--gap-xs);
}

.footer-brand a {
    color: var(--accent-primary);
    text-decoration: none;
    font-weight: 600;
    transition: color var(--transition-fast);
}

.footer-brand a:hover {
    color: var(--accent-secondary);
}

.donate-btn {
    display: inline-flex;
    align-items: center;
    gap: var(--gap-sm);
    background: linear-gradient(135deg, #0070ba, #003087);
    color: #fff;
    padding: var(--gap-sm) var(--gap-lg);
    border-radius: var(--radius-md);
    text-decoration: none;
    font-size: 0.875rem;
    font-weight: 600;
    transition: all var(--transition-normal);
    box-shadow: var(--shadow-md);
}

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

.donate-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(0, 112, 186, 0.4);
}

/* ==========================================
   RESPONSIVE DESIGN
   ========================================== */
@media (max-width: 480px) {
    .app-container {
        padding: var(--gap-sm);
    }

    .logo-text {
        font-size: 1.25rem;
        letter-spacing: 2px;
    }

    .logo-icon {
        width: 36px;
        height: 36px;
        font-size: 1.25rem;
    }

    .stats-bar {
        padding: var(--gap-sm) var(--gap-md);
    }

    .cell {
        font-size: 1.25rem;
    }

    .cell .note {
        font-size: 0.45rem;
    }

    .num-btn {
        padding: var(--gap-sm);
        font-size: 1.125rem;
    }

    .action-btn {
        padding: var(--gap-sm) var(--gap-md);
        min-width: 70px;
    }

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

    .action-btn span {
        font-size: 0.65rem;
    }
}

@media (max-width: 360px) {
    .cell {
        font-size: 1rem;
    }

    .num-btn {
        font-size: 1rem;
        padding: var(--gap-xs);
    }

    .action-buttons {
        gap: var(--gap-sm);
    }

    .action-btn {
        min-width: 60px;
        padding: var(--gap-xs) var(--gap-sm);
    }
}

/* ==========================================
   ANIMATIONS
   ========================================== */
@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

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

.game-container {
    animation: slideUp 0.5s ease;
}

/* Number completion animation */
.num-btn.completed {
    animation: pulse 0.5s ease;
}

@keyframes pulse {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.1); }
}

/* ==========================================
   CONFETTI ANIMATION
   ========================================== */
.confetti-container {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    overflow: hidden;
    z-index: 100;
}

.confetti {
    position: absolute;
    width: 10px;
    height: 10px;
    opacity: 0;
}

.confetti.active {
    animation: confetti-fall 3s ease-out forwards;
}

@keyframes confetti-fall {
    0% {
        opacity: 1;
        transform: translateY(0) rotate(0deg);
    }
    100% {
        opacity: 0;
        transform: translateY(100vh) rotate(720deg);
    }
}

/* Star burst effect for win */
.win-icon::before,
.win-icon::after {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 120px;
    height: 120px;
    background: radial-gradient(circle, rgba(63, 185, 80, 0.4) 0%, transparent 70%);
    border-radius: 50%;
    transform: translate(-50%, -50%);
    animation: star-pulse 2s ease-in-out infinite;
}

.win-icon::after {
    animation-delay: 1s;
    width: 140px;
    height: 140px;
}

@keyframes star-pulse {
    0%, 100% {
        transform: translate(-50%, -50%) scale(0.8);
        opacity: 0;
    }
    50% {
        transform: translate(-50%, -50%) scale(1.2);
        opacity: 1;
    }
}

/* Enhanced win overlay */
.win-overlay.active .win-icon {
    animation: win-bounce 0.6s ease;
}

@keyframes win-bounce {
    0% { transform: scale(0); }
    50% { transform: scale(1.2); }
    70% { transform: scale(0.9); }
    100% { transform: scale(1); }
}

/* Game over shake */
.gameover-overlay.active .gameover-icon {
    animation: gameover-shake 0.5s ease;
}

@keyframes gameover-shake {
    0%, 100% { transform: translateX(0); }
    20%, 60% { transform: translateX(-10px); }
    40%, 80% { transform: translateX(10px); }
}

/* ==========================================
   HEADER USER DISPLAY & CONTROLS
   ========================================== */
.user-display {
    display: flex;
    align-items: center;
    gap: var(--gap-xs);
    padding: var(--gap-xs) var(--gap-sm);
    background: var(--bg-tertiary);
    border: 1px solid var(--cell-border);
    border-radius: var(--radius-md);
}

.user-icon {
    display: flex;
    align-items: center;
    justify-content: center;
}

.user-icon svg {
    width: 18px;
    height: 18px;
    color: var(--text-muted);
}

.user-display.logged-in .user-icon svg {
    color: var(--accent-primary);
}

.user-name {
    font-size: 0.8rem;
    color: var(--text-secondary);
    max-width: 80px;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.user-display.logged-in .user-name {
    color: var(--accent-primary);
    font-weight: 500;
}

.header-btn {
    background: var(--bg-tertiary);
    border: 1px solid var(--cell-border);
    border-radius: var(--radius-md);
    padding: var(--gap-sm) var(--gap-md);
    color: var(--text-secondary);
    font-size: 0.8rem;
    cursor: pointer;
    transition: all var(--transition-normal);
    display: flex;
    align-items: center;
    gap: var(--gap-xs);
}

.header-btn svg {
    width: 18px;
    height: 18px;
}

.header-btn:hover {
    background: var(--bg-elevated);
    border-color: var(--accent-primary);
    color: var(--text-primary);
}

/* ==========================================
   MODAL OVERLAY
   ========================================== */
.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(13, 17, 23, 0.9);
    backdrop-filter: blur(8px);
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-normal);
    z-index: 100;
    padding: var(--gap-md);
}

.modal-overlay.active {
    opacity: 1;
    visibility: visible;
}

.modal-content {
    background: var(--bg-secondary);
    border: 1px solid var(--cell-border);
    border-radius: var(--radius-lg);
    padding: var(--gap-xl);
    width: 100%;
    max-width: 360px;
    position: relative;
    transform: scale(0.9) translateY(20px);
    transition: transform var(--transition-normal);
    box-shadow: var(--shadow-lg);
}

.modal-overlay.active .modal-content {
    transform: scale(1) translateY(0);
}

.modal-content.modal-large {
    max-width: 500px;
}

.modal-close {
    position: absolute;
    top: var(--gap-md);
    right: var(--gap-md);
    background: none;
    border: none;
    color: var(--text-muted);
    font-size: 1.5rem;
    cursor: pointer;
    line-height: 1;
    padding: 0;
    width: 30px;
    height: 30px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
}

.modal-close:hover {
    background: var(--bg-elevated);
    color: var(--text-primary);
}

.modal-title {
    font-family: 'Armata', sans-serif;
    font-size: 1.25rem;
    color: var(--text-primary);
    margin-bottom: var(--gap-lg);
    text-align: center;
    letter-spacing: 1px;
}

/* ==========================================
   LOGIN FORM
   ========================================== */
.login-form {
    display: flex;
    flex-direction: column;
    gap: var(--gap-md);
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: var(--gap-xs);
}

.form-group label {
    font-size: 0.8rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.form-group input {
    background: var(--bg-tertiary);
    border: 1px solid var(--cell-border);
    border-radius: var(--radius-sm);
    padding: var(--gap-sm) var(--gap-md);
    font-size: 1rem;
    color: var(--text-primary);
    transition: all var(--transition-fast);
    font-family: inherit;
}

.form-group input::placeholder {
    color: var(--text-muted);
}

.form-group input:focus {
    outline: none;
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px var(--accent-glow);
}

.form-error {
    color: var(--accent-error);
    font-size: 0.8rem;
    min-height: 1.2em;
    text-align: center;
}

.form-buttons {
    display: flex;
    gap: var(--gap-sm);
    margin-top: var(--gap-sm);
}

.form-buttons .btn {
    flex: 1;
    padding: var(--gap-md);
}

.btn-secondary {
    background: var(--bg-tertiary);
    border: 1px solid var(--cell-border);
    color: var(--text-secondary);
}

.btn-secondary:hover {
    background: var(--bg-elevated);
    color: var(--text-primary);
    border-color: var(--accent-primary);
}

/* ==========================================
   LEADERBOARD
   ========================================== */
.leaderboard-container {
    max-height: 400px;
    overflow-y: auto;
}

.leaderboard-table {
    width: 100%;
    border-collapse: collapse;
}

.leaderboard-table th,
.leaderboard-table td {
    padding: var(--gap-sm) var(--gap-sm);
    text-align: center;
    border-bottom: 1px solid var(--cell-border);
}

.leaderboard-table th {
    font-size: 0.7rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    font-weight: 600;
    position: sticky;
    top: 0;
    background: var(--bg-secondary);
}

.leaderboard-table td {
    font-size: 0.9rem;
    color: var(--text-primary);
}

.leaderboard-table tbody tr:hover {
    background: var(--bg-tertiary);
}

.leaderboard-table .rank-1 td:first-child {
    color: #ffd700;
    font-weight: 700;
}

.leaderboard-table .rank-2 td:first-child {
    color: #c0c0c0;
    font-weight: 700;
}

.leaderboard-table .rank-3 td:first-child {
    color: #cd7f32;
    font-weight: 700;
}

.difficulty-badge {
    display: inline-block;
    padding: 2px 8px;
    border-radius: var(--radius-sm);
    font-size: 0.7rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.difficulty-badge.easy {
    background: rgba(63, 185, 80, 0.2);
    color: var(--accent-success);
}

.difficulty-badge.medium {
    background: rgba(210, 153, 34, 0.2);
    color: var(--accent-warning);
}

.difficulty-badge.hard {
    background: rgba(248, 81, 73, 0.2);
    color: var(--accent-error);
}

.leaderboard-empty {
    text-align: center;
    color: var(--text-muted);
    padding: var(--gap-xl);
    font-style: italic;
}

.leaderboard-table:not(.empty) + .leaderboard-empty {
    display: none;
}

/* Scrollbar for leaderboard */
.leaderboard-container::-webkit-scrollbar {
    width: 6px;
}

.leaderboard-container::-webkit-scrollbar-track {
    background: var(--bg-tertiary);
    border-radius: 3px;
}

.leaderboard-container::-webkit-scrollbar-thumb {
    background: var(--bg-elevated);
    border-radius: 3px;
}

.leaderboard-container::-webkit-scrollbar-thumb:hover {
    background: var(--accent-primary);
}

/* ==========================================
   RESPONSIVE - HEADER CONTROLS
   ========================================== */
@media (max-width: 480px) {
    .header-controls {
        gap: var(--gap-xs);
    }

    .user-display {
        padding: var(--gap-xs);
    }

    .user-name {
        max-width: 50px;
        font-size: 0.7rem;
    }

    .header-btn {
        padding: var(--gap-xs) var(--gap-sm);
        font-size: 0.7rem;
    }

    .header-btn svg {
        width: 16px;
        height: 16px;
    }

    .modal-content {
        padding: var(--gap-lg);
    }

    .leaderboard-table th,
    .leaderboard-table td {
        padding: var(--gap-xs);
        font-size: 0.75rem;
    }

    .difficulty-badge {
        font-size: 0.6rem;
        padding: 2px 4px;
    }
}