@import url('https://fonts.googleapis.com/css2?family=Nanum+Gothic:wght@400;700&family=Orbitron:wght@400;700&display=swap');

:root {
    --bg-color: #1a1a1a;
    --text-color: #f0f0f0;
    --app-bg: rgba(0, 0, 0, 0.5);
    --accent-color: #00e5ff;
    --secondary-accent: #007bff;
    --box-shadow: rgba(0, 123, 255, 0.5);
    --border-color: rgba(0, 123, 255, 0.3);
    --button-text: #f0f0f0;
}

body.light-mode {
    --bg-color: #f8f9fa;
    --text-color: #212529;
    --app-bg: rgba(255, 255, 255, 0.9);
    --accent-color: #007bff;
    --secondary-accent: #0056b3;
    --box-shadow: rgba(0, 0, 0, 0.15);
    --border-color: rgba(0, 0, 0, 0.1);
    --button-text: #ffffff;
}

body {
    background: var(--bg-color);
    color: var(--text-color);
    font-family: 'Nanum Gothic', sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    padding: 20px;
    transition: background 0.3s, color 0.3s;
}

#app {
    width: 100%;
    max-width: 900px;
    text-align: center;
    background: var(--app-bg);
    padding: 50px;
    border-radius: 20px;
    box-shadow: 0 0 30px var(--box-shadow);
    border: 1px solid var(--border-color);
    backdrop-filter: blur(10px);
    transition: background 0.3s, box-shadow 0.3s, border 0.3s;
}

h1 {
    font-family: 'Orbitron', sans-serif;
    font-size: 4rem;
    color: var(--accent-color);
    letter-spacing: 2px;
    margin-bottom: 30px;
    text-shadow: 0 0 15px var(--box-shadow);
    transition: color 0.3s;
}

.button-container {
    display: flex;
    justify-content: center;
    gap: 30px;
    margin-top: 40px;
}

.button {
    display: inline-block;
    padding: 18px 35px;
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--button-text);
    background: linear-gradient(45deg, var(--secondary-accent), var(--accent-color));
    border: none;
    border-radius: 15px;
    text-decoration: none;
    transition: all 0.3s ease;
    box-shadow: 0 0 15px var(--box-shadow);
}

.button:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 20px var(--box-shadow);
}

.numbers-container {
    display: flex;
    justify-content: center;
    gap: 15px;
    margin: 40px 0;
}

.number {
    width: 70px;
    height: 70px;
    line-height: 70px;
    font-size: 2.5rem;
    font-weight: bold;
    color: var(--bg-color);
    background: var(--accent-color);
    border-radius: 50%;
    box-shadow: 0 0 15px var(--box-shadow);
}

#generate-btn {
    padding: 15px 30px;
    font-size: 1.2rem;
    font-weight: bold;
    color: var(--button-text);
    background: var(--secondary-accent);
    border: none;
    border-radius: 10px;
    cursor: pointer;
    transition: background-color 0.3s;
}

#generate-btn:hover {
    background-color: var(--secondary-accent);
    filter: brightness(1.2);
}

.back-link {
    display: inline-block;
    margin-top: 30px;
    color: var(--accent-color);
    text-decoration: none;
    font-size: 1.2rem;
    font-weight: bold;
}

.back-link:hover {
    text-decoration: underline;
}

#theme-toggle {
    position: fixed;
    top: 20px;
    right: 20px;
    padding: 10px 15px;
    font-size: 1.5rem;
    background: var(--app-bg);
    border: 1px solid var(--border-color);
    border-radius: 50%;
    cursor: pointer;
    box-shadow: 0 0 10px var(--box-shadow);
    z-index: 1000;
    transition: all 0.3s;
}

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