:root {
    --main-bg-color: #f8f9fa;
    --container-bg-color: #ffffff;
    --primary-color: #4a90e2;
    --secondary-color: #50e3c2;
    --text-color: #333333;
    --shadow-color: rgba(0, 0, 0, 0.1);
    --button-glow: rgba(74, 144, 226, 0.5);
}

[data-theme="dark"] {
    --main-bg-color: #1a1a1a;
    --container-bg-color: #2d2d2d;
    --primary-color: #61a0e9;
    --secondary-color: #6ef1d6;
    --text-color: #f0f0f0;
    --shadow-color: rgba(0, 0, 0, 0.4);
    --button-glow: rgba(97, 160, 233, 0.6);
}

body {
    font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, system-ui, Roboto, 'Helvetica Neue', 'Segoe UI', 'Apple SD Gothic Neo', 'Noto Sans KR', 'Malgun Gothic', sans-serif;
    background-color: var(--main-bg-color);
    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 18c3.866 0 7-3.134 7-7s-3.134-7-7-7-7 3.134-7 7 3.134 7 7 7zm48 25c3.866 0 7-3.134 7-7s-3.134-7-7-7-7 3.134-7 7 3.134 7 7 7zm-43-7c1.657 0 3-1.343 3-3s-1.343-3-3-3-3 1.343-3 3 1.343 3 3 3zm63 31c1.657 0 3-1.343 3-3s-1.343-3-3-3-3 1.343-3 3 1.343 3 3 3zM34 90c1.657 0 3-1.343 3-3s-1.343-3-3-3-3 1.343-3 3 1.343 3 3 3zm56-76c1.657 0 3-1.343 3-3s-1.343-3-3-3-3 1.343-3 3 1.343 3 3 3zM12 86c2.21 0 4-1.79 4-4s-1.79-4-4-4-4 1.79-4 4 1.79 4 4 4zm13-56c2.21 0 4-1.79 4-4s-1.79-4-4-4-4 1.79-4 4 1.79 4 4 4zm43 6c2.21 0 4-1.79 4-4s-1.79-4-4-4-4 1.79-4 4 1.79 4 4 4zm-4-64c2.21 0 4-1.79 4-4s-1.79-4-4-4-4 1.79-4 4 1.79 4 4 4zm-3 23c-2.76 0-5 2.24-5 5s2.24 5 5 5 5-2.24 5-5-2.24-5-5-5zm-34 53c-2.76 0-5 2.24-5 5s2.24 5 5 5 5-2.24 5-5-2.24-5-5-5zm60-31c-2.76 0-5 2.24-5 5s2.24 5 5 5 5-2.24 5-5-2.24-5-5-5z" id="a" fill-opacity="0.05" fill="%234a90e2"/%3E%3Cuse xlink:href="%23a" x="-100"/%3E%3Cuse xlink:href="%23a" y="-100"/%3E%3Cuse xlink:href="%23a" x="-100" y="-100"/%3E%3C/svg%3E');
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    transition: background-color 0.3s ease;
}

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

.theme-toggle button {
    background: var(--container-bg-color);
    border: 2px solid var(--primary-color);
    color: var(--text-color);
    padding: 10px 15px;
    border-radius: 20px;
    cursor: pointer;
    font-weight: bold;
    transition: all 0.3s ease;
}

.theme-toggle button:hover {
    background: var(--primary-color);
    color: white;
}

.container {
    position: relative;
    text-align: center;
    background-color: var(--container-bg-color);
    padding: 40px;
    border-radius: 24px;
    box-shadow: 0 20px 40px var(--shadow-color);
    transition: background-color 0.3s ease, box-shadow 0.3s ease;
    max-width: 500px;
    width: 90%;
}

h1 {
    color: var(--text-color);
    font-size: 2.2em;
    margin-bottom: 30px;
    font-weight: 800;
}


.numbers-container {
    display: flex;
    justify-content: center;
    gap: 15px;
    margin-bottom: 30px;
    flex-wrap: wrap;
}

.number-circle {
    width: 60px;
    height: 60px;
    border-radius: 50%;
    background-color: var(--primary-color);
    color: white;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.8em;
    font-weight: bold;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
    transition: transform 0.3s ease, background-color 0.3s ease;
}

#generate-button {
    background-image: linear-gradient(45deg, var(--primary-color), var(--secondary-color));
    color: white;
    border: none;
    padding: 15px 30px;
    font-size: 1.2em;
    font-weight: bold;
    border-radius: 50px;
    cursor: pointer;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
}

#generate-button:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(74, 144, 226, 0.5);
}

#generate-button:active {
    transform: translateY(0);
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
}

.divider {
    border: 0;
    height: 1px;
    background: var(--shadow-color);
    margin: 40px 0;
}

.contact-section {
    text-align: left;
}

.contact-section h2 {
    color: var(--text-color);
    font-size: 1.5em;
    margin-bottom: 20px;
    font-weight: 700;
}

#contact-form {
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.form-group label {
    font-size: 0.9em;
    font-weight: 600;
    color: var(--text-color);
    opacity: 0.8;
}

input, textarea {
    background: var(--main-bg-color);
    border: 1px solid var(--shadow-color);
    color: var(--text-color);
    padding: 12px 15px;
    border-radius: 12px;
    font-size: 1em;
    font-family: inherit;
    transition: border-color 0.3s ease, box-shadow 0.3s ease;
}

input:focus, textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px var(--button-glow);
}

.submit-button {
    background: var(--primary-color);
    color: white;
    border: none;
    padding: 12px;
    border-radius: 12px;
    font-size: 1em;
    font-weight: bold;
    cursor: pointer;
    transition: background 0.3s ease, transform 0.2s ease;
    margin-top: 10px;
}

.submit-button:hover {
    background: var(--secondary-color);
    transform: translateY(-2px);
}

.submit-button:active {
    transform: translateY(0);
}