:root {
    --bg-color: #f0f2f5;
    --text-color: #333;
    --container-bg: #fff;
    --primary-color: #007bff;
    --primary-hover: #0056b3;
    --border-color: #eee;
    --shadow-color: rgba(0, 0, 0, 0.1);
}

.dark-mode {
    --bg-color: #18191a;
    --text-color: #e4e6eb;
    --container-bg: #242526;
    --primary-color: #4da3ff;
    --primary-hover: #357abd;
    --border-color: #3e4042;
    --shadow-color: rgba(0, 0, 0, 0.3);
}

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

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

.container {
    background-color: var(--container-bg);
    padding: 2rem;
    border-radius: 1rem;
    box-shadow: 0 4px 6px var(--shadow-color);
    text-align: center;
    position: relative;
    max-width: 500px;
    width: 90%;
}

h1 {
    margin-bottom: 1.5rem;
    color: var(--primary-color);
}

.number-display {
    display: flex;
    justify-content: center;
    margin-bottom: 2rem;
}

#generate-btn {
    background-color: var(--primary-color);
    color: #fff;
    border: none;
    padding: 0.75rem 1.5rem;
    border-radius: 0.5rem;
    font-size: 1rem;
    cursor: pointer;
    transition: background-color 0.3s ease;
}

#generate-btn:hover {
    background-color: var(--primary-hover);
}

.history {
    margin-top: 2rem;
}

#history-list {
    list-style: none;
    padding: 0;
    max-height: 200px;
    overflow-y: auto;
}

#history-list li {
    padding: 0.5rem;
    border-bottom: 1px solid var(--border-color);
}

.contact-form {
    margin-top: 2rem;
    padding-top: 2rem;
    border-top: 1px solid var(--border-color);
    text-align: left;
}

.contact-form h2 {
    text-align: center;
    margin-bottom: 1.5rem;
    color: var(--primary-color);
}

.form-group {
    margin-bottom: 1rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: bold;
    font-size: 0.9rem;
}

.form-group input,
.form-group textarea {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: 0.5rem;
    background-color: var(--bg-color);
    color: var(--text-color);
    font-family: inherit;
    font-size: 1rem;
}

.form-group textarea {
    height: 100px;
    resize: vertical;
}

.submit-btn {
    width: 100%;
    background-color: var(--primary-color);
    color: #fff;
    border: none;
    padding: 0.75rem;
    border-radius: 0.5rem;
    font-size: 1rem;
    cursor: pointer;
    transition: background-color 0.3s;
    font-weight: bold;
}

.submit-btn:hover {
    background-color: var(--primary-hover);
}

#theme-toggle {
    position: absolute;
    top: 1rem;
    right: 1rem;
    background: none;
    border: 1px solid var(--border-color);
    padding: 0.5rem;
    border-radius: 0.5rem;
    cursor: pointer;
    color: var(--text-color);
    font-size: 1.2rem;
    display: flex;
    align-items: center;
    justify-content: center;
}

@media (max-width: 480px) {
    .container {
        padding: 1.5rem;
    }
}