:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --secondary-color: #64748b;
    --success-color: #10b981;
    --success-hover: #059669;
    --error-color: #ef4444;
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --border-color: #cbd5e1;
    --border-dark: #64748b;
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Helvetica Neue', Arial, sans-serif;
    background: linear-gradient(135deg, #f8fafc 0%, #e2e8f0 100%);
    color: var(--text-primary);
    height: 100vh;
    overflow: hidden;
    display: flex;
    flex-direction: column;
    padding: 1.5rem;
}

header {
    text-align: center;
    margin-bottom: 1.5rem;
    flex-shrink: 0;
}

header h1 {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.25rem;
    letter-spacing: -0.025em;
}

header .subtitle {
    font-size: 0.875rem;
    color: var(--text-secondary);
    font-weight: 500;
}

#container {
    display: flex;
    align-items: stretch;
    gap: 2rem;
    max-width: 1400px;
    margin: 0 auto;
    flex: 1;
    min-height: 0;
    overflow: hidden;
}

#crossword-container {
    position: relative;
    display: flex;
    flex-direction: column;
    background: var(--bg-primary);
    padding: 2rem;
    border-radius: 16px;
    box-shadow: var(--shadow-lg);
    flex-shrink: 0;
}

#crossword-image {
    position: absolute;
    top: 2rem;
    left: 2rem;
    z-index: 2;
    pointer-events: none;
    border-radius: 4px;
}

#grid {
    position: relative;
    z-index: 1;
    display: grid;
    border: 2px solid var(--border-dark);
    border-radius: 4px;
    overflow: hidden;
    grid-template-columns: repeat(auto-fill, 32px);
    grid-auto-rows: 32px;
    grid-gap: 0;
    box-shadow: var(--shadow-md);
}

.cell {
    width: 32px;
    height: 32px;
    border: 1px solid var(--border-color);
    box-sizing: border-box;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 18px;
    font-family: 'SF Mono', 'Monaco', 'Consolas', 'Courier New', monospace;
    position: relative;
    background-color: var(--bg-primary);
    transition: background-color 0.15s ease;    will-change: background-color;}

.cell:focus-within {
    background-color: #dbeafe;
    border-color: var(--primary-color);
    z-index: 10;
}

.cell.black {
    background-color: var(--text-primary);
    border-color: var(--text-primary);
}

.cell .number {
    position: absolute;
    top: 2px;
    left: 2px;
    font-size: 9px;
    font-weight: 600;
    color: var(--text-secondary);
    line-height: 1;
    z-index: 3;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', sans-serif;
}

.cell input {
    width: 100%;
    height: 100%;
    border: none;
    text-align: center;
    text-transform: uppercase;
    font-size: 18px;
    font-weight: 500;
    font-family: 'SF Mono', 'Monaco', 'Consolas', 'Courier New', monospace;
    background: transparent;
    color: var(--text-primary);
    outline: none;
}

.cell input:disabled {
    color: var(--text-secondary);
    cursor: not-allowed;
}

#clues {
    display: flex;
    flex-direction: row;
    gap: 1.5rem;
    flex: 1;
    max-width: 900px;
    min-height: 0;
    overflow: hidden;
}

#across-clues, #down-clues {
    background: var(--bg-primary);
    padding: 1.5rem;
    border-radius: 12px;
    box-shadow: var(--shadow-md);
    flex: 1;
    display: flex;
    flex-direction: column;
    min-height: 0;
    overflow: hidden;
}

#across-clues h2, #down-clues h2 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 1rem;
    padding-bottom: 0.75rem;
    border-bottom: 2px solid var(--bg-tertiary);
    flex-shrink: 0;
}

#across-list, #down-list {
    list-style: none;
    flex: 1;
    overflow-y: auto;
    min-height: 0;
}

#across-list li, #down-list li {
    padding: 0.75rem 0;
    border-bottom: 1px solid var(--bg-tertiary);
    font-size: 0.875rem;
    line-height: 1.5;
    color: var(--text-secondary);
}

#across-list li:last-child, #down-list li:last-child {
    border-bottom: none;
}

#across-list li strong, #down-list li strong {
    color: var(--primary-color);
    font-weight: 600;
    margin-right: 0.5rem;
}

#check-container {
    margin-top: 2rem;
    text-align: center;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
}

#buttons-row {
    display: flex;
    gap: 1rem;
    align-items: center;
}

#check-btn {
    padding: 0.875rem 2.5rem;
    font-size: 1rem;
    font-weight: 600;
    background: linear-gradient(135deg, var(--success-color) 0%, var(--success-hover) 100%);
    color: white;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    box-shadow: var(--shadow-md);
    transition: all 0.2s ease;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    will-change: transform, box-shadow;
}

#check-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

#check-btn:active {
    transform: translateY(0);
}

#hint-btn {
    padding: 0.875rem 2.5rem;
    font-size: 1rem;
    font-weight: 600;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-hover) 100%);
    color: white;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    box-shadow: var(--shadow-md);
    transition: all 0.2s ease;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    will-change: transform, box-shadow;
}

#hint-btn:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

#hint-btn:active:not(:disabled) {
    transform: translateY(0);
}

#hint-btn:disabled {
    background: linear-gradient(135deg, #9ca3af 0%, #6b7280 100%);
    cursor: not-allowed;
    transform: none;
    box-shadow: var(--shadow-sm);
}

#completed-msg {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--success-color);
    padding: 1rem 2rem;
    background: #d1fae5;
    border-radius: 8px;
    border: 2px solid var(--success-color);
    box-shadow: var(--shadow-md);
}

.cell.incorrect {
    animation: blink-red 0.5s 2;
}

.cell.hinted {
    animation: blink-blue 0.5s 2;
}

@keyframes blink-red {
    0%, 100% { 
        background-color: var(--bg-primary); 
    }
    50% { 
        background-color: #fee2e2;
        border-color: var(--error-color);
    }
}

@keyframes blink-blue {
    0%, 100% { 
        background-color: var(--bg-primary); 
    }
    50% { 
        background-color: #dbeafe;
        border-color: var(--primary-color);
    }
}

/* Custom scrollbar */
#across-list, #down-list {
    scrollbar-width: thin;
    scrollbar-color: var(--border-color) var(--bg-tertiary);
}

#across-list::-webkit-scrollbar,
#down-list::-webkit-scrollbar {
    width: 8px;
}

#across-list::-webkit-scrollbar-track,
#down-list::-webkit-scrollbar-track {
    background: var(--bg-tertiary);
    border-radius: 4px;
}

#across-list::-webkit-scrollbar-thumb,
#down-list::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 4px;
}

#across-list::-webkit-scrollbar-thumb:hover,
#down-list::-webkit-scrollbar-thumb:hover {
    background: var(--border-dark);
}

/* Responsive design */
@media (max-width: 1024px) {
    #container {
        flex-direction: column;
        gap: 1.5rem;
    }
    
    #clues {
        max-width: 100%;
        flex-direction: column;
    }
}

@media (max-width: 640px) {
    body {
        padding: 0.75rem;
    }
    
    header {
        margin-bottom: 1rem;
    }
    
    header h1 {
        font-size: 1.5rem;
    }
    
    header .subtitle {
        font-size: 0.75rem;
    }
    
    #container {
        gap: 1rem;
    }
    
    #crossword-container {
        padding: 1rem;
    }
    
    #clues {
        gap: 1rem;
    }
    
    #across-clues, #down-clues {
        padding: 1rem;
    }
}