:root {
    --bg-gradient: linear-gradient(135deg, #1d2671, #c33764);
    --container-bg: rgba(255, 255, 255, 0.1);
    --text-color: white;
    --button-bg: white;
    --button-text: #c33764;
    --shadow: rgba(0, 0, 0, 0.3);
}

[data-theme="dark"] {
    --bg-gradient: linear-gradient(135deg, #0f0c29, #302b63, #24243e);
    --container-bg: rgba(0, 0, 0, 0.3);
    --text-color: #e0e0e0;
    --button-bg: #c33764;
    --button-text: white;
    --shadow: rgba(0, 0, 0, 0.6);
}

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

body {
    font-family: "Pretendard", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background: var(--bg-gradient);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    color: var(--text-color);
    padding: 20px;
    transition: all 0.5s ease;
}

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

#theme-btn {
    background: var(--container-bg);
    backdrop-filter: blur(5px);
    border: 1px solid var(--text-color);
    color: var(--text-color);
    padding: 8px 16px;
    border-radius: 20px;
    cursor: pointer;
    font-size: 14px;
    transition: 0.3s;
}

.container {
    width: 100%;
    max-width: 900px;
    background: var(--container-bg);
    backdrop-filter: blur(10px);
    border-radius: 20px;
    padding: 40px;
    text-align: center;
    box-shadow: 0 8px 30px var(--shadow);
    transition: background 0.5s ease;
}

h1 {
    font-size: 42px;
    margin-bottom: 10px;
}

p {
    opacity: 0.9;
    margin-bottom: 30px;
}

#generate-btn {
    background: var(--button-bg);
    color: var(--button-text);
    border: none;
    padding: 16px 32px;
    border-radius: 12px;
    font-size: 18px;
    font-weight: bold;
    cursor: pointer;
    transition: 0.3s;
    margin-bottom: 40px;
}

#generate-btn:hover {
    transform: translateY(-3px);
    opacity: 0.9;
}

.set {
    margin-bottom: 25px;
    animation: fadeIn 0.5s ease;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.set-title {
    margin-bottom: 12px;
    font-size: 20px;
    font-weight: bold;
}

.numbers {
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 12px;
}

.ball {
    width: 60px;
    height: 60px;
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 22px;
    font-weight: bold;
    color: white;
    box-shadow: 0 4px 10px rgba(0,0,0,0.2);
    animation: pop 0.4s ease;
}

@keyframes pop {
    from { transform: scale(0.3); opacity: 0; }
    to { transform: scale(1); opacity: 1; }
}

.yellow { background: #fbc531; }
.blue { background: #3498db; }
.red { background: #e84118; }
.gray { background: #7f8c8d; }
.green { background: #2ecc71; }

.info {
    margin-top: 30px;
    font-size: 14px;
    opacity: 0.8;
}