:root {
    --bg-color: #f8fafc;
    --card-bg: #ffffff;
    --text-color: #1e293b;
    --accent-color: #3b82f6;
    --accent-glow: rgba(59, 130, 246, 0.5);
    --secondary-bg: #f1f5f9;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --shadow-glow: 0 0 15px var(--accent-glow);
    --border-color: #e2e8f0;
    --transition-speed: 0.3s;

    /* Lotto Ball Colors */
    --ball-1: #facc15; /* 1-10 */
    --ball-11: #60a5fa; /* 11-20 */
    --ball-21: #f87171; /* 21-30 */
    --ball-31: #94a3b8; /* 31-40 */
    --ball-41: #4ade80; /* 41-45 */
}

[data-theme='dark'] {
    --bg-color: #0f172a;
    --card-bg: #1e293b;
    --text-color: #f1f5f9;
    --secondary-bg: #334155;
    --border-color: #334155;
    --accent-glow: rgba(59, 130, 246, 0.3);
}

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

body {
    font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    transition: background-color var(--transition-speed), color var(--transition-speed);
    padding: 2rem 1rem;
}

.app-container {
    width: 100%;
    max-width: 600px;
    background-color: var(--card-bg);
    padding: 2.5rem;
    border-radius: 24px;
    box-shadow: var(--shadow-lg);
    border: 1px solid var(--border-color);
    position: relative;
    overflow: hidden;
}

.app-container::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, #3b82f6, #8b5cf6, #ec4899);
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
}

h1 {
    font-size: 1.75rem;
    font-weight: 800;
    letter-spacing: -0.025em;
    background: linear-gradient(135deg, #3b82f6, #8b5cf6);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.theme-toggle {
    background: var(--secondary-bg);
    border: none;
    color: var(--text-color);
    padding: 0.5rem;
    border-radius: 12px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s;
    border: 1px solid var(--border-color);
}

.theme-toggle:hover {
    transform: scale(1.1);
    background: var(--border-color);
}

.sets-container {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    margin-bottom: 2.5rem;
}

.number-set {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.25rem;
    background-color: var(--secondary-bg);
    border-radius: 16px;
    transition: transform 0.2s;
    border: 1px solid transparent;
}

.number-set:hover {
    transform: translateY(-2px);
    border-color: var(--accent-glow);
    box-shadow: var(--shadow-md);
}

.set-label {
    font-weight: 700;
    font-size: 0.875rem;
    color: var(--text-color);
    opacity: 0.6;
    margin-right: 1rem;
    min-width: 20px;
}

.balls {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
    justify-content: center;
}

.ball {
    width: 42px;
    height: 42px;
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    font-weight: 800;
    font-size: 1.125rem;
    color: white;
    text-shadow: 0 1px 2px rgba(0,0,0,0.2);
    box-shadow: 0 4px 6px rgba(0,0,0,0.1), inset 0 -2px 4px rgba(0,0,0,0.2), inset 0 2px 4px rgba(255,255,255,0.3);
    transition: transform 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);
}

.ball:hover {
    transform: scale(1.1) rotate(5deg);
}

.ball.range-1 { background-color: var(--ball-1); color: #854d0e; }
.ball.range-11 { background-color: var(--ball-11); }
.ball.range-21 { background-color: var(--ball-21); }
.ball.range-31 { background-color: var(--ball-31); }
.ball.range-41 { background-color: var(--ball-41); }

#generate-btn {
    width: 100%;
    padding: 1rem;
    font-size: 1.125rem;
    font-weight: 700;
    border: none;
    background: linear-gradient(135deg, #3b82f6, #2563eb);
    color: white;
    border-radius: 16px;
    cursor: pointer;
    transition: all 0.2s;
    box-shadow: 0 4px 14px 0 var(--accent-glow);
}

#generate-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(59, 130, 246, 0.4);
}

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

@media (max-width: 480px) {
    .app-container {
        padding: 1.5rem;
    }
    
    .number-set {
        flex-direction: column;
        gap: 0.75rem;
    }
    
    .set-label {
        margin-right: 0;
        margin-bottom: 0.25rem;
    }

    .ball {
        width: 36px;
        height: 36px;
        font-size: 1rem;
    }
}