/* ==========================================================================
   Stylesheet: styles.css
   Purpose: Modern Sudoku UI Design System, Glassmorphism, Side-by-Side Layout
   Author: Praful Kumar
   Website: https://prafulkr.xyz/
   LinkedIn: https://www.linkedin.com/in/prafulkr/
   Email: jobspraful@gmail.com
   Created On: 05/08/2026
   ========================================================================== */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=Outfit:wght@400;500;600;700;800&display=swap');

:root {
    /* Color Palette - Vibrant UI Reference Glassmorphism */
    --bg-gradient: #0d1127;
    --card-bg: linear-gradient(135deg, rgba(255, 255, 255, 0.22) 0%, rgba(255, 255, 255, 0.08) 100%);
    --card-border: rgba(255, 255, 255, 0.4);
    --card-shadow: 0 16px 40px 0 rgba(0, 0, 0, 0.25), inset 0 1px 1px 0 rgba(255, 255, 255, 0.6), inset 0 -1px 1px 0 rgba(0, 0, 0, 0.15);
    
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    
    --accent-indigo: #6366f1;
    --accent-indigo-hover: #4f46e5;
    --accent-violet: #8b5cf6;
    --accent-cyan: #06b6d4;
    --accent-emerald: #10b981;
    --accent-rose: #f43f5e;
    --accent-amber: #f59e0b;

    /* Board & Cell Colors */
    --board-bg: #0f1322;
    --board-border: #475569;
    --cell-bg: #151a2e;
    --cell-given-text: #f8fafc;
    --cell-user-text: #818cf8;
    --cell-border: rgba(255, 255, 255, 0.04);
    --cell-selected: rgba(99, 102, 241, 0.35);
    --cell-highlight: rgba(99, 102, 241, 0.12);
    --cell-same-num: rgba(139, 92, 246, 0.25);
    --cell-error-bg: rgba(244, 63, 94, 0.25);
    --cell-error-text: #fda4af;
    --cell-hint-bg: rgba(16, 185, 129, 0.3);
    --cell-hint-text: #34d399;
    --note-text: #94a3b8;

    /* Spacing & Sizes */
    --radius-sm: 8px;
    --radius-md: 14px;
    --radius-lg: 20px;
    --radius-xl: 28px;

    --font-heading: 'Outfit', sans-serif;
    --font-body: 'Inter', sans-serif;
}

[data-theme="light"] {
    --bg-gradient: radial-gradient(circle at 50% 0%, #f1f5f9 0%, #e2e8f0 100%);
    --card-bg: rgba(255, 255, 255, 0.85);
    --card-border: rgba(0, 0, 0, 0.08);
    --card-shadow: 0 20px 40px rgba(0, 0, 0, 0.08);
    
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-muted: #94a3b8;

    --board-bg: #ffffff;
    --board-border: #94a3b8;
    --cell-bg: #f8fafc;
    --cell-given-text: #0f172a;
    --cell-user-text: #4338ca;
    --cell-border: rgba(0, 0, 0, 0.06);
    --cell-selected: rgba(99, 102, 241, 0.25);
    --cell-highlight: rgba(99, 102, 241, 0.08);
    --cell-same-num: rgba(139, 92, 246, 0.18);
    --cell-error-bg: rgba(244, 63, 94, 0.15);
    --cell-error-text: #e11d48;
    --cell-hint-bg: rgba(16, 185, 129, 0.2);
    --cell-hint-text: #059669;
    --note-text: #64748b;
}

/* ==========================================================================
   Base & Reset
   ========================================================================== */

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    user-select: none;
    -webkit-user-select: none;
}

body {
    font-family: var(--font-body);
    background-color: #0d1127;
    background-image: 
        radial-gradient(circle at 10% 10%, rgba(0, 212, 255, 0.45) 0%, transparent 45%),
        radial-gradient(circle at 90% 10%, rgba(147, 51, 234, 0.45) 0%, transparent 45%),
        radial-gradient(circle at 85% 85%, rgba(236, 72, 153, 0.4) 0%, transparent 45%),
        radial-gradient(circle at 15% 85%, rgba(59, 130, 246, 0.45) 0%, transparent 45%),
        linear-gradient(135deg, #09132e 0%, #170d38 50%, #0a1f38 100%);
    background-attachment: fixed;
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: space-between;
    overflow-x: hidden;
    transition: background 0.3s ease, color 0.3s ease;
}

.app-container {
    width: 90%;
    max-width: 940px;
    padding: 20px 0;
    display: flex;
    flex-direction: column;
    gap: 20px;
    margin: 0 auto;
}

/* ==========================================================================
   Header Section
   ========================================================================== */

.app-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px 20px;
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    backdrop-filter: blur(16px);
    border-radius: var(--radius-lg);
    box-shadow: var(--card-shadow);
}

.brand {
    display: flex;
    align-items: center;
    gap: 10px;
}

.brand-icon {
    width: 40px;
    height: 40px;
    background: linear-gradient(135deg, var(--accent-indigo), var(--accent-violet));
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    color: #fff;
    font-family: var(--font-heading);
    font-size: 1.4rem;
    font-weight: 800;
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.4);
}

.brand-text h1 {
    font-family: var(--font-heading);
    font-size: 1.5rem;
    font-weight: 700;
    letter-spacing: -0.5px;
    background: linear-gradient(135deg, var(--text-primary), var(--text-secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.brand-text p {
    font-size: 0.75rem;
    color: var(--text-muted);
    font-weight: 500;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 10px;
}

.icon-btn {
    width: 40px;
    height: 40px;
    border-radius: var(--radius-md);
    border: 1px solid var(--card-border);
    background: rgba(255, 255, 255, 0.05);
    color: var(--text-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: 1.1rem;
    transition: all 0.2s ease;
}

.icon-btn:hover {
    background: rgba(99, 102, 241, 0.15);
    border-color: var(--accent-indigo);
    transform: translateY(-2px);
}

/* ==========================================================================
   Difficulty Selector & Status Bar
   ========================================================================== */

.controls-top {
    display: flex;
    flex-direction: column;
    gap: 14px;
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    backdrop-filter: blur(16px);
    padding: 16px;
    border-radius: var(--radius-lg);
    box-shadow: var(--card-shadow);
}

.difficulty-selector {
    display: flex;
    justify-content: space-between;
    gap: 6px;
    background: rgba(0, 0, 0, 0.15);
    padding: 4px;
    border-radius: var(--radius-md);
}

.diff-btn {
    flex: 1;
    padding: 8px 4px;
    border: none;
    border-radius: var(--radius-sm);
    background: transparent;
    color: var(--text-secondary);
    font-family: var(--font-heading);
    font-size: 0.78rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    text-align: center;
}

.diff-btn:hover {
    color: var(--text-primary);
    background: rgba(255, 255, 255, 0.05);
}

.diff-btn.active {
    background: linear-gradient(135deg, var(--accent-indigo), var(--accent-violet));
    color: #fff;
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.3);
}

.status-bar {
    display: flex;
    justify-content: space-around;
    align-items: center;
    padding-top: 6px;
    border-top: 1px solid var(--card-border);
}

.status-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 2px;
}

.status-label {
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.8px;
    color: var(--text-muted);
    font-weight: 600;
}

.status-value {
    font-family: var(--font-heading);
    font-size: 1.15rem;
    font-weight: 700;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 6px;
}

.status-value i {
    font-size: 0.95rem;
    color: var(--accent-indigo);
}

/* ==========================================================================
   Main Game Area: Side-by-Side Layout
   ========================================================================== */

.game-area {
    display: grid;
    grid-template-columns: 1fr 340px;
    gap: 20px;
    align-items: start;
    width: 100%;
}

/* ==========================================================================
   Sudoku Board Grid Container (Left Side)
   ========================================================================== */

.board-container {
    position: relative;
    width: 100%;
    max-width: 540px;
    margin: 0 auto;
    aspect-ratio: 1 / 1;
    background: var(--board-bg);
    border: 3px solid var(--board-border);
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--card-shadow);
}

.sudoku-board {
    display: grid;
    grid-template-columns: repeat(9, 1fr);
    grid-template-rows: repeat(9, 1fr);
    width: 100%;
    height: 100%;
}

.cell {
    position: relative;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--cell-bg);
    border: 1px solid var(--cell-border);
    font-family: var(--font-heading);
    font-size: 1.6rem;
    font-weight: 700;
    cursor: pointer;
    transition: background 0.15s ease, transform 0.1s ease, color 0.15s ease;
}

/* 3x3 Block Thicker Borders */
.cell[data-col="2"],
.cell[data-col="5"] {
    border-right: 3px solid var(--board-border);
}

.cell[data-row="2"],
.cell[data-row="5"] {
    border-bottom: 3px solid var(--board-border);
}

/* Cell States */
.cell.given {
    color: var(--cell-given-text);
    font-weight: 800;
}

.cell.user-filled {
    color: var(--cell-user-text);
}

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

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

.cell.selected {
    background: var(--cell-selected) !important;
    box-shadow: inset 0 0 0 2px var(--accent-indigo);
    z-index: 2;
}

.cell.error {
    background: var(--cell-error-bg) !important;
    color: var(--cell-error-text) !important;
    animation: shake 0.3s ease;
}

.cell.hint-highlight {
    background: var(--cell-hint-bg) !important;
    color: var(--cell-hint-text) !important;
    animation: pulseGlow 0.6s ease infinite alternate;
}

/* Pencil Candidate Notes */
.notes-grid {
    position: absolute;
    top: 2px;
    left: 2px;
    right: 2px;
    bottom: 2px;
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    grid-template-rows: repeat(3, 1fr);
    pointer-events: none;
}

.note-num {
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.65rem;
    font-weight: 600;
    color: var(--note-text);
    font-family: var(--font-body);
}

/* Pause Overlay */
.pause-overlay {
    position: absolute;
    inset: 0;
    background: rgba(15, 19, 34, 0.92);
    backdrop-filter: blur(12px);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 16px;
    z-index: 10;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.3s ease;
}

.pause-overlay.active {
    opacity: 1;
    pointer-events: auto;
}

.pause-overlay h2 {
    font-family: var(--font-heading);
    font-size: 2rem;
    color: var(--text-primary);
}

/* ==========================================================================
   Side Panel: 3x3 Keypad Numpad & Actions (Right Side)
   ========================================================================== */

.side-panel {
    display: flex;
    flex-direction: column;
    gap: 16px;
    width: 100%;
}

.side-card {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    backdrop-filter: blur(16px);
    padding: 16px;
    border-radius: var(--radius-lg);
    box-shadow: var(--card-shadow);
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.side-card-header {
    display: flex;
    align-items: center;
    gap: 8px;
    font-family: var(--font-heading);
    font-size: 0.88rem;
    font-weight: 700;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    padding-bottom: 8px;
    border-bottom: 1px solid var(--card-border);
}

.side-card-header i {
    color: var(--accent-indigo);
}

/* 3x3 Numpad Keypad */
.numpad-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 10px;
}

.num-btn {
    aspect-ratio: 1 / 1;
    border: 1px solid var(--card-border);
    border-radius: var(--radius-md);
    background: rgba(255, 255, 255, 0.05);
    color: var(--text-primary);
    font-family: var(--font-heading);
    font-size: 1.5rem;
    font-weight: 800;
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.15);
}

.num-btn:hover {
    background: linear-gradient(135deg, var(--accent-indigo), var(--accent-violet));
    color: #fff;
    transform: translateY(-3px);
    box-shadow: 0 6px 16px rgba(99, 102, 241, 0.4);
}

.num-btn.completed {
    opacity: 0.25;
    pointer-events: none;
}

/* Action Tools Grid */
.action-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 8px;
}

.action-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 4px;
    padding: 10px 4px;
    border: 1px solid var(--card-border);
    border-radius: var(--radius-md);
    background: rgba(255, 255, 255, 0.04);
    color: var(--text-secondary);
    font-family: var(--font-body);
    font-size: 0.72rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
}

.action-btn i {
    font-size: 1.1rem;
}

.action-btn:hover {
    background: rgba(99, 102, 241, 0.15);
    border-color: var(--accent-indigo);
    color: var(--text-primary);
    transform: translateY(-2px);
}

.action-btn.active {
    background: linear-gradient(135deg, var(--accent-indigo), var(--accent-violet));
    color: #fff;
    border-color: transparent;
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.3);
}

/* ==========================================================================
   Victory / Win Modal
   ========================================================================== */

.modal-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.75);
    backdrop-filter: blur(8px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 100;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.3s ease;
}

.modal-overlay.active {
    opacity: 1;
    pointer-events: auto;
}

.modal-card {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: var(--radius-xl);
    padding: 32px 28px;
    width: 90%;
    max-width: 440px;
    text-align: center;
    box-shadow: 0 25px 50px rgba(0, 0, 0, 0.5);
    transform: scale(0.9);
    transition: transform 0.3s ease;
}

.modal-overlay.active .modal-card {
    transform: scale(1);
}

.modal-badge {
    width: 70px;
    height: 70px;
    margin: 0 auto 16px;
    background: linear-gradient(135deg, var(--accent-emerald), var(--accent-cyan));
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    color: #fff;
    box-shadow: 0 10px 25px rgba(16, 185, 129, 0.4);
}

.modal-card h2 {
    font-family: var(--font-heading);
    font-size: 1.8rem;
    margin-bottom: 8px;
}

.modal-card p {
    color: var(--text-secondary);
    font-size: 0.95rem;
    margin-bottom: 20px;
}

.modal-stats {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 12px;
    background: rgba(0, 0, 0, 0.2);
    padding: 16px;
    border-radius: var(--radius-md);
    margin-bottom: 24px;
}

.btn-primary {
    padding: 12px 28px;
    background: linear-gradient(135deg, var(--accent-indigo), var(--accent-violet));
    color: #fff;
    border: none;
    border-radius: var(--radius-md);
    font-family: var(--font-heading);
    font-size: 1rem;
    font-weight: 700;
    cursor: pointer;
    box-shadow: 0 6px 20px rgba(99, 102, 241, 0.4);
    transition: all 0.2s ease;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 25px rgba(99, 102, 241, 0.5);
}

/* ==========================================================================
   Footer Component
   ========================================================================== */

.app-footer {
    width: 100%;
    max-width: 900px;
    margin: 20px auto 10px;
    padding: 20px;
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    backdrop-filter: blur(16px);
    border-radius: var(--radius-lg);
    box-shadow: var(--card-shadow);
    display: flex;
    flex-direction: column;
    gap: 16px;
    text-align: center;
}

.footer-credit {
    font-size: 0.95rem;
    color: var(--text-secondary);
    font-weight: 500;
}

.footer-link-highlight {
    color: var(--accent-indigo);
    font-weight: 700;
    text-decoration: none;
    transition: color 0.2s ease;
}

.footer-link-highlight:hover {
    color: var(--accent-violet);
    text-decoration: underline;
}

.footer-links {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 10px;
    flex-wrap: wrap;
    font-size: 0.84rem;
}

.footer-link {
    color: var(--text-secondary);
    text-decoration: none;
    display: inline-flex;
    align-items: center;
    gap: 5px;
    transition: color 0.2s ease;
}

.footer-link:hover {
    color: var(--accent-indigo);
}

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

.tech-badges {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 8px;
    flex-wrap: wrap;
}

.badge {
    padding: 4px 10px;
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--card-border);
    border-radius: 20px;
    font-size: 0.72rem;
    font-weight: 600;
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    gap: 5px;
}

.badge i {
    color: var(--accent-violet);
}

.footer-bottom {
    font-size: 0.75rem;
    color: var(--text-muted);
    border-top: 1px solid var(--card-border);
    padding-top: 12px;
}

/* Keyframes */
@keyframes shake {
    0%, 100% { transform: translateX(0); }
    20%, 60% { transform: translateX(-4px); }
    40%, 80% { transform: translateX(4px); }
}

@keyframes pulseGlow {
    from { box-shadow: inset 0 0 0 2px var(--accent-emerald); }
    to { box-shadow: inset 0 0 12px var(--accent-emerald); }
}

/* Responsive adjustments */
@media (max-width: 768px) {
    .game-area {
        grid-template-columns: 1fr;
    }
    .side-panel {
        display: grid;
        grid-template-columns: 1fr 1fr;
        gap: 12px;
    }
}

@media (max-width: 520px) {
    .app-container {
        padding: 12px 10px;
    }
    .side-panel {
        grid-template-columns: 1fr;
    }
    .cell {
        font-size: 1.3rem;
    }
    .num-btn {
        font-size: 1.25rem;
    }
    .action-btn {
        font-size: 0.65rem;
        padding: 8px 2px;
    }
}