:root {
    --background-color: oklch(98.5% 0.01 240);
    --text-color: oklch(20% 0.05 240);
    --primary-color: oklch(60% 0.2 265);
    --accent-color: oklch(70% 0.25 290);
    --surface-color: oklch(99.9% 0 0);
    --shadow-color: oklch(20% 0.05 240 / 15%);
    --secondary-btn-bg: oklch(90% 0.01 240);
    --secondary-btn-text: oklch(40% 0.1 240);
    --border-color: oklch(90% 0.01 240);
    --stats-bg: oklch(97% 0.01 240);
    --footer-text: oklch(60% 0.05 240);

    --font-sans: 'Nanum Gothic', system-ui, -apple-system, BlinkMacSystemFont, 
                 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
}

[data-theme="dark"] {
    --background-color: oklch(15% 0.02 240);
    --text-color: oklch(90% 0.01 240);
    --primary-color: oklch(70% 0.15 265);
    --accent-color: oklch(80% 0.2 290);
    --surface-color: oklch(25% 0.03 240);
    --shadow-color: oklch(0% 0 0 / 50%);
    --secondary-btn-bg: oklch(35% 0.04 240);
    --secondary-btn-text: oklch(85% 0.02 240);
    --border-color: oklch(40% 0.04 240);
    --stats-bg: oklch(30% 0.04 240);
    --footer-text: oklch(75% 0.02 240);
}

body {
    font-family: var(--font-sans);
    background-color: var(--background-color);
    color: var(--text-color);
    display: grid;
    place-items: center;
    min-height: 100vh;
    margin: 0;
    padding: 1rem 0;
    transition: background-color 0.3s ease, color 0.3s ease;
    background-image: repeating-radial-gradient(circle at center center, transparent 0px, transparent 12px,rgba(0,0,0,0.03) 12px, rgba(0,0,0,0.03) 24px);
}

[data-theme="dark"] body {
    background-image: repeating-radial-gradient(circle at center center, transparent 0px, transparent 12px,rgba(255,255,255,0.02) 12px, rgba(255,255,255,0.02) 24px);
}

#app {
    width: clamp(320px, 90vw, 500px);
    background-color: var(--surface-color);
    border-radius: 28px;
    padding: 2.5rem;
    box-shadow: 0 20px 60px -15px var(--shadow-color);
    text-align: center;
    position: relative;
    animation: fadeIn 0.6s ease-out forwards;
    transition: background-color 0.3s ease, box-shadow 0.3s ease;
}

/* Theme Toggle Button */
.theme-toggle {
    position: absolute;
    top: 1.5rem;
    right: 1.5rem;
    background: var(--secondary-btn-bg);
    border: none;
    border-radius: 50%;
    width: 44px;
    height: 44px;
    display: grid;
    place-items: center;
    cursor: pointer;
    color: var(--secondary-btn-text);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: 0 4px 10px -4px var(--shadow-color);
}

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

.theme-toggle .icon {
    width: 24px;
    height: 24px;
}

[data-theme="dark"] .sun-icon { display: block; }
[data-theme="dark"] .moon-icon { display: none; }
.sun-icon { display: none; }
.moon-icon { display: block; }

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(25px); }
    to { opacity: 1; transform: translateY(0); }
}

h1 {
    font-size: clamp(2.2rem, 5vw, 2.8rem);
    font-weight: 800;
    color: var(--primary-color);
    margin: 0 0 0.5rem;
    letter-spacing: -0.05em;
    transition: color 0.3s ease;
}

p {
    font-size: clamp(1rem, 2.5vw, 1.1rem);
    line-height: 1.7;
    margin: 0 0 1.5rem;
}

.button-group {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 0.75rem;
    margin-bottom: 2rem;
}

.button {
    border: none;
    border-radius: 16px;
    padding: 1rem 2rem;
    font-size: 1.1rem;
    font-weight: 700;
    cursor: pointer;
    transition: transform 0.25s cubic-bezier(0.175, 0.885, 0.32, 1.275), box-shadow 0.25s ease-out, background-color 0.3s ease, color 0.3s ease;
    will-change: transform, box-shadow;
    display: inline-flex;
    align-items: center;
    gap: 0.6rem;
    justify-content: center;
}

.icon {
    width: 1.2em;
    height: 1.2em;
}

#generate-btn {
    background-image: linear-gradient(45deg, var(--primary-color), var(--accent-color));
    color: white;
    box-shadow: 0 4px 15px -4px var(--shadow-color);
}

#generate-btn:hover {
    transform: translateY(-4px);
    box-shadow: 0 12px 25px -6px var(--shadow-color), 0 0 0 4px oklch(from var(--accent-color) calc(l / 1.2) c h / 30%);
}

.secondary-btn {
    background-color: var(--secondary-btn-bg);
    color: var(--secondary-btn-text);
    box-shadow: 0 4px 10px -4px var(--shadow-color);
}

.secondary-btn:hover {
    transform: translateY(-4px);
    background-color: oklch(from var(--secondary-btn-bg) calc(l - 5) c h);
    box-shadow: 0 10px 20px -8px var(--shadow-color);
}

section h2 {
    font-size: 1.6rem;
    font-weight: 700;
    color: var(--text-color);
    margin: 3rem 0 1.5rem;
    border-top: 1px solid var(--border-color);
    padding-top: 2rem;
    transition: color 0.3s ease, border-color 0.3s ease;
}

#numbers-display {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 1.2rem;
    min-height: 70px;
    margin-top: 1rem;
}

.number-ball {
    width: 64px;
    height: 64px;
    border-radius: 50%;
    display: grid;
    place-items: center;
    font-size: 1.6rem;
    font-weight: 700;
    color: white;
    box-shadow: inset 0 -6px 12px rgb(0 0 0 / 25%), 0 5px 10px -5px var(--shadow-color);
    animation: popIn 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275) forwards;
    transform-origin: bottom;
}

#stats-display {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(30px, 1fr));
    gap: 0.5rem;
    align-items: flex-end;
    min-height: 150px;
    padding: 1rem;
    background-color: var(--stats-bg);
    border-radius: 12px;
    transition: background-color 0.3s ease;
}

.stat-bar {
    background-color: var(--primary-color);
    border-radius: 4px;
    transition: height 0.3s ease-out, background-color 0.3s ease;
    position: relative;
}

.stat-bar:hover .tooltip {
    opacity: 1;
    transform: translateY(-5px);
}

.tooltip {
    position: absolute;
    top: -30px;
    left: 50%;
    transform: translateX(-50%);
    background-color: var(--text-color);
    color: var(--surface-color);
    padding: 0.3rem 0.6rem;
    border-radius: 6px;
    font-size: 0.9rem;
    opacity: 0;
    transition: opacity 0.2s, transform 0.2s, background-color 0.3s ease, color 0.3s ease;
    white-space: nowrap;
}

#saved-list {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.saved-item {
    background-color: var(--surface-color);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 1rem 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    animation: slideIn 0.4s ease-out;
    transition: background-color 0.3s ease, border-color 0.3s ease;
}

@keyframes slideIn {
    from { opacity: 0; transform: translateX(-20px); }
    to { opacity: 1; transform: translateX(0); }
}

.saved-numbers-set {
    display: flex;
    gap: 0.5rem;
}

.saved-number {
    font-weight: 700;
    font-size: 1.1rem;
}

.delete-btn {
    background: none;
    border: none;
    color: oklch(60% 0.1 15);
    cursor: pointer;
    font-size: 1.2rem;
    transition: color 0.2s ease;
    padding: 0.5rem;
}

.delete-btn:hover {
    color: oklch(50% 0.2 15);
}

.delete-btn .icon {
    width: 1em;
    height: 1em;
}


footer {
    margin-top: 3rem;
    font-size: 0.9rem;
    color: var(--footer-text);
    transition: color 0.3s ease;
}