:root {
    --font-family: 'Noto Sans KR', sans-serif;
    --background-start: oklch(0.95 0.05 250);
    --background-end: oklch(0.85 0.1 280);
    --text-color: oklch(0.2 0.05 250);
    --shadow-color: oklch(0.5 0.1 280 / 0.5);
    --button-bg: oklch(0.6 0.2 280);
    --button-hover-bg: oklch(0.65 0.2 280);
    --button-text-color: oklch(0.98 0.01 280);
    --container-bg: oklch(1 0 0 / 0.1);
    --container-border: oklch(1 0 0 / 0.2);
}

body.dark-mode {
    --background-start: oklch(0.15 0.02 250);
    --background-end: oklch(0.1 0.05 280);
    --text-color: oklch(0.95 0.02 250);
    --shadow-color: oklch(0 0 0 / 0.8);
    --button-bg: oklch(0.4 0.15 280);
    --button-hover-bg: oklch(0.45 0.15 280);
    --container-bg: oklch(0 0 0 / 0.4);
    --container-border: oklch(1 0 0 / 0.1);
}

body {
    font-family: var(--font-family);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    background: linear-gradient(135deg, var(--background-start), var(--background-end));
    background-attachment: fixed;
    color: var(--text-color);
    overflow: hidden;
    position: relative;
    transition: background 0.3s ease, color 0.3s ease;
}

body::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-image: url('data:image/svg+xml,%3Csvg width="100" height="100" viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg"%3E%3Cpath d="M11 18.277L18.277 11 88.243 81.046 81.046 88.243zM81.046 11L11 81.046l7.231 7.197L88.243 18.23z" fill="%239C92AC" fill-opacity="0.05" fill-rule="evenodd"/%3E%3C/svg%3E');
    opacity: 0.3;
    z-index: -1;
}

.container {
    text-align: center;
    background: var(--container-bg);
    padding: 2.5rem 4rem;
    border-radius: 20px;
    backdrop-filter: blur(10px);
    box-shadow: 0 15px 30px var(--shadow-color);
    border: 1px solid var(--container-border);
    transition: background 0.3s ease, border 0.3s ease, box-shadow 0.3s ease;
}

h1 {
    font-size: 2.5rem;
    margin-bottom: 2rem;
    font-weight: 700;
    text-shadow: 0 2px 5px oklch(0 0 0 / 0.1);
}

#numbers-container {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 2.5rem;
    perspective: 800px;
}

.number-circle {
    width: 60px;
    height: 60px;
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.8rem;
    font-weight: 700;
    color: white;
    box-shadow: 0 5px 15px var(--shadow-color);
    transition: transform 0.3s ease, background-color 0.3s ease, box-shadow 0.3s ease;
    transform-style: preserve-3d;
    animation: appear 0.5s backwards;
}

@keyframes appear {
    from {
        transform: scale(0) rotateY(180deg);
        opacity: 0;
    }
    to {
        transform: scale(1) rotateY(0deg);
        opacity: 1;
    }
}


#generate-btn {
    padding: 1rem 2rem;
    font-size: 1.2rem;
    font-family: var(--font-family);
    font-weight: 700;
    color: var(--button-text-color);
    background: var(--button-bg);
    border: none;
    border-radius: 50px;
    cursor: pointer;
    transition: transform 0.2s ease, box-shadow 0.2s ease, background-color 0.2s ease;
    box-shadow: 0 5px 15px oklch(0.6 0.2 280 / 0.4);
}

#generate-btn:hover {
    transform: translateY(-3px);
    background: var(--button-hover-bg);
    box-shadow: 0 8px 20px oklch(0.65 0.2 280 / 0.5);
}

#generate-btn:active {
    transform: translateY(0);
    box-shadow: 0 5px 15px oklch(0.6 0.2 280 / 0.4);
}

.theme-toggle-container {
    position: absolute;
    top: 20px;
    right: 20px;
}

#theme-toggle-btn {
    background: var(--container-bg);
    border: 1px solid var(--container-border);
    color: var(--text-color);
    padding: 8px 16px;
    border-radius: 20px;
    cursor: pointer;
    font-size: 0.9rem;
    font-family: var(--font-family);
    font-weight: 700;
    backdrop-filter: blur(10px);
    transition: all 0.3s ease;
    display: flex;
    justify-content: center;
    align-items: center;
}

#theme-toggle-btn:hover {
    transform: scale(1.1);
}