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

:root {
    --bg-gradient-start: #667eea;
    --bg-gradient-end: #764ba2;
    --container-bg: #ffffff;
    --text-primary: #333333;
    --text-secondary: #666666;
    --color-x: #ef4444;
    --color-o: #3b82f6;
    --board-bg: #333333;
    --cell-bg: #f5f5f5;
    --cell-border: #dddddd;
    --cell-hover: #e0e0e0;
    --shadow: rgba(0, 0, 0, 0.3);
}

body.dark-mode {
    --bg-gradient-start: #000000;
    --bg-gradient-end: #1a1a1a;
    --container-bg: #1a1a1a;
    --text-primary: #ffffff;
    --text-secondary: #b0b0b0;
    --color-x: #ef4444;
    --color-o: #3b82f6;
    --board-bg: #000000;
    --cell-bg: #2a2a2a;
    --cell-border: #404040;
    --cell-hover: #3a3a3a;
    --shadow: rgba(0, 0, 0, 0.8);
}

html {
    overflow-y: auto;
}

body {
    font-family: Arial, sans-serif;
    min-height: 100vh;
    background: linear-gradient(135deg, var(--bg-gradient-start) 0%, var(--bg-gradient-end) 100%);
    padding: 2rem 1rem;
    transition: background 0.3s ease;
    position: relative;
    display: flex;
    flex-direction: column;
    align-items: center;
}

#particles {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 0;
    pointer-events: none;
}

.theme-toggle {
    position: fixed;
    top: 1.5rem;
    right: 1.5rem;
    width: 60px;
    height: 60px;
    border-radius: 50%;
    border: none;
    background: var(--container-bg);
    box-shadow: 0 4px 15px var(--shadow);
    cursor: pointer;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.5rem;
    transition: all 0.3s ease;
    z-index: 1000;
}

.theme-toggle:hover {
    transform: scale(1.1) rotate(15deg);
}

.theme-toggle:active {
    transform: scale(0.95);
}

.sun-icon {
    display: block;
}

.moon-icon {
    display: none;
}

body.dark-mode .sun-icon {
    display: none;
}

body.dark-mode .moon-icon {
    display: block;
}

.container {
    text-align: center;
    background: var(--container-bg);
    padding: 2rem;
    border-radius: 1rem;
    box-shadow: 0 10px 30px var(--shadow);
    transition: all 0.3s ease;
    position: relative;
    z-index: 1;
}

h1 {
    color: var(--text-primary);
    margin-bottom: 1rem;
    font-size: 1.8rem;
    transition: color 0.3s ease;
}

.info {
    margin-bottom: 1.5rem;
}

.status {
    font-size: 1.2rem;
    color: var(--color-x);
    font-weight: bold;
    margin-bottom: 0.5rem;
    transition: color 0.3s ease;
}

.instructions {
    font-size: 0.9rem;
    color: var(--text-secondary);
    transition: color 0.3s ease;
}

.difficulty-selector {
    margin-top: 1rem;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.difficulty-selector label {
    font-size: 0.95rem;
    color: var(--text-primary);
    font-weight: 500;
    transition: color 0.3s ease;
}

.difficulty-selector select {
    padding: 0.5rem 1rem;
    font-size: 0.95rem;
    border: 2px solid var(--cell-border);
    border-radius: 0.5rem;
    background: var(--cell-bg);
    color: var(--text-primary);
    cursor: pointer;
    transition: all 0.3s ease;
    outline: none;
}

.difficulty-selector select:hover {
    border-color: var(--color-x);
}

.difficulty-selector select:focus {
    border-color: var(--color-o);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.main-board {
    display: grid;
    grid-template-columns: repeat(3, 200px);
    grid-template-rows: repeat(3, 200px);
    gap: 12px;
    margin: 0 auto 1.5rem;
    background: var(--board-bg);
    padding: 12px;
    border-radius: 1rem;
    transition: background 0.3s ease;
}

.mini-board {
    background: var(--container-bg);
    border-radius: 0.5rem;
    padding: 8px;
    position: relative;
    aspect-ratio: 1;
    transition: background 0.3s ease;
    width: 200px;
    height: 200px;
}

.mini-board.won {
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 5rem;
    font-weight: bold;
    pointer-events: none;
}

.mini-board.won.x {
    background: linear-gradient(135deg, var(--color-x) 0%, #dc2626 100%);
    color: white;
}

.mini-board.won.o {
    background: linear-gradient(135deg, var(--color-o) 0%, #2563eb 100%);
    color: white;
}

.mini-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    grid-template-rows: repeat(3, 1fr);
    gap: 4px;
    height: 100%;
}

.mini-cell {
    background: var(--cell-bg);
    border: 2px solid var(--cell-border);
    border-radius: 0.3rem;
    font-size: 2rem;
    font-weight: bold;
    cursor: pointer;
    display: flex;
    justify-content: center;
    align-items: center;
    transition: all 0.2s ease;
}

.mini-cell:hover:not(.taken) {
    background: var(--cell-hover);
    transform: scale(1.05);
}

.mini-cell.taken {
    cursor: not-allowed;
}

.mini-cell.x {
    color: var(--color-x);
}

.mini-cell.o {
    color: var(--color-o);
}

.reset-btn {
    padding: 0.75rem 2rem;
    font-size: 1rem;
    background: #667eea;
    color: white;
    border: none;
    border-radius: 0.5rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

.reset-btn:hover {
    background: #5568d3;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px var(--shadow);
}

.github-star {
    position: fixed;
    bottom: 1.5rem;
    right: 1.5rem;
    background: var(--container-bg);
    color: var(--text-primary);
    text-decoration: none;
    padding: 0.6rem 1.2rem;
    border-radius: 2rem;
    font-size: 0.9rem;
    font-weight: bold;
    box-shadow: 0 4px 15px var(--shadow);
    transition: all 0.3s ease;
    z-index: 1000;
    display: flex;
    align-items: center;
    gap: 0.4rem;
}

.github-star:hover {
    transform: translateY(-3px);
    box-shadow: 0 6px 20px var(--shadow);
}

.star-count {
    background: var(--cell-bg);
    border: 1px solid var(--cell-border);
    padding: 0.1rem 0.5rem;
    border-radius: 1rem;
    font-size: 0.8rem;
}

.winner-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.8);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000;
}

.winner-message {
    background: white;
    padding: 3rem;
    border-radius: 1rem;
    text-align: center;
}

.winner-message h2 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    color: var(--color-x);
}

@media (max-width: 768px) {
    body {
        padding: 0.5rem;
    }
    
    .container {
        padding: 1rem;
        max-width: 100%;
    }
    
    h1 {
        font-size: 1.4rem;
        margin-bottom: 0.75rem;
    }
    
    .info {
        margin-bottom: 1rem;
    }
    
    .status {
        font-size: 1rem;
    }
    
    .instructions {
        font-size: 0.8rem;
    }
    
    .difficulty-selector {
        flex-direction: column;
        gap: 0.3rem;
    }
    
    .difficulty-selector label {
        font-size: 0.85rem;
    }
    
    .difficulty-selector select {
        padding: 0.4rem 0.8rem;
        font-size: 0.85rem;
        width: 100%;
        max-width: 200px;
    }
    
    .main-board {
        grid-template-columns: repeat(3, 1fr);
        grid-template-rows: repeat(3, 1fr);
        gap: 8px;
        padding: 8px;
        max-width: 100%;
        width: calc(100vw - 2rem);
    }
    
    .mini-board {
        width: 100%;
        height: 100%;
        padding: 4px;
    }
    
    .mini-grid {
        gap: 3px;
    }
    
    .mini-cell {
        font-size: 1.2rem;
    }
    
    .mini-board.won {
        font-size: 2.5rem;
    }
    
    .reset-btn {
        padding: 0.6rem 1.5rem;
        font-size: 0.9rem;
    }
    
    .theme-toggle {
        width: 50px;
        height: 50px;
        font-size: 1.2rem;
        top: 0.75rem;
        right: 0.75rem;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0.75rem;
    }
    
    h1 {
        font-size: 1.2rem;
    }
    
    .status {
        font-size: 0.9rem;
    }
    
    .instructions {
        font-size: 0.75rem;
    }
    
    .main-board {
        gap: 6px;
        padding: 6px;
        width: calc(100vw - 1.5rem);
    }
    
    .mini-board {
        padding: 3px;
    }
    
    .mini-grid {
        gap: 2px;
    }
    
    .mini-cell {
        font-size: 1rem;
        border-width: 1px;
    }
    
    .mini-board.won {
        font-size: 2rem;
    }
    
    .reset-btn {
        padding: 0.5rem 1.2rem;
        font-size: 0.85rem;
    }
    
    .theme-toggle {
        width: 45px;
        height: 45px;
        font-size: 1.1rem;
        top: 0.5rem;
        right: 0.5rem;
    }
}

@media (max-width: 360px) {
    h1 {
        font-size: 1.1rem;
    }
    
    .main-board {
        gap: 5px;
        padding: 5px;
        width: calc(100vw - 1rem);
    }
    
    .mini-cell {
        font-size: 0.9rem;
    }
    
    .mini-board.won {
        font-size: 1.8rem;
    }
}