:root {
    /* Light Theme (Default) */
    --bg-color: oklch(95% 0.01 280);
    --container-bg: oklch(100% 0 0);
    --text-color: oklch(25% 0.01 280);
    --primary-color: oklch(50% 0.15 280);
    --primary-hover: oklch(40% 0.15 280);
    --secondary-bg: oklch(90% 0.02 280);
    --border-color: oklch(85% 0.01 280);
    --success-color: oklch(75% 0.15 150);
    --error-color: oklch(60% 0.2 25);
    --shadow-color: rgba(0, 0, 0, 0.1);
    --gradient: linear-gradient(135deg, oklch(90% 0.05 280), oklch(95% 0.05 320));
    --card-shadow: 0 10px 30px var(--shadow-color);
}

[data-theme="dark"] {
    /* Dark Theme */
    --bg-color: oklch(15% 0.02 280);
    --container-bg: oklch(20% 0.02 280);
    --text-color: oklch(95% 0.01 280);
    --primary-color: oklch(70% 0.1 280);
    --primary-hover: oklch(80% 0.1 280);
    --secondary-bg: oklch(25% 0.03 280);
    --border-color: oklch(35% 0.03 280);
    --shadow-color: rgba(0, 0, 0, 0.4);
    --gradient: linear-gradient(135deg, oklch(10% 0.02 280), oklch(15% 0.02 300));
}

* {
    box-sizing: border-box;
    transition: background-color 0.3s ease, color 0.3s ease, border-color 0.3s ease, box-shadow 0.3s ease;
}

body {
    font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, system-ui, Roboto, sans-serif;
    background: var(--gradient);
    background-attachment: fixed;
    color: var(--text-color);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
}

.container {
    background-color: var(--container-bg);
    padding: 2.5rem;
    border-radius: 24px;
    box-shadow: var(--card-shadow);
    text-align: center;
    max-width: 500px;
    width: 90%;
    position: relative;
    border: 1px solid var(--border-color);
}

/* Theme Toggle Button */
.theme-toggle {
    position: absolute;
    top: 1.5rem;
    right: 1.5rem;
    background: var(--secondary-bg);
    border: none;
    width: 40px;
    height: 40px;
    border-radius: 12px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    color: var(--text-color);
    box-shadow: 0 4px 10px var(--shadow-color);
}

.theme-toggle:hover {
    transform: scale(1.05);
}

h1 {
    color: var(--primary-color);
    margin-bottom: 2rem;
    font-size: 1.8rem;
    letter-spacing: -0.5px;
}

h2 {
    color: var(--primary-color);
    border-bottom: 2px solid var(--border-color);
    padding-bottom: 0.5rem;
    margin-bottom: 1.5rem;
    font-size: 1.2rem;
    text-align: left;
}

.number-display {
    display: flex;
    justify-content: center;
    gap: 12px;
    margin-bottom: 2rem;
    flex-wrap: wrap;
}

.number-display div {
    width: 44px;
    height: 44px;
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 50%;
    background-color: var(--secondary-bg);
    font-weight: 700;
    font-size: 1.1rem;
    color: var(--text-color);
    box-shadow: 0 4px 8px var(--shadow-color);
}

.winning-numbers .number-display div {
    background-color: var(--success-color);
    color: oklch(100% 0 0);
}

.number-grid {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    gap: 8px;
    margin-bottom: 2rem;
}

.number-grid button {
    aspect-ratio: 1;
    border: 1px solid var(--border-color);
    border-radius: 12px;
    background-color: var(--container-bg);
    color: var(--text-color);
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    font-size: 0.9rem;
    font-weight: 500;
}

.number-grid button:hover {
    background-color: var(--secondary-bg);
}

.number-grid button.selected {
    background-color: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px var(--primary-color);
}

button#generate-btn, button#check-btn {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 1rem 2rem;
    border-radius: 14px;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 600;
    transition: all 0.2s ease;
    width: 100%;
    margin-top: 0.5rem;
    box-shadow: 0 6px 15px var(--shadow-color);
}

button#generate-btn:hover, button#check-btn:hover {
    background-color: var(--primary-hover);
    transform: translateY(-1px);
}

.result {
    margin: 2rem 0;
    padding: 1rem;
    background-color: var(--secondary-bg);
    border-radius: 16px;
}

#result-text {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--error-color);
    margin: 0;
}