:root {
    --bg-color: #f0f2f5;
    --bg-pattern-color: #e0e4e8;
    --container-bg: #ffffff;
    --text-color: #2c3e50;
    --shadow-color: rgba(0,0,0,0.1);
    --button-bg: #4CAF50;
    --button-hover-bg: #45a049;
}

body.dark-mode {
    --bg-color: #1a1a1a;
    --bg-pattern-color: #252525;
    --container-bg: #2d2d2d;
    --text-color: #ecf0f1;
    --shadow-color: rgba(0,0,0,0.5);
    --button-bg: #2ecc71;
    --button-hover-bg: #27ae60;
}

body {
    font-family: 'Helvetica Neue', sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    background-color: var(--bg-color);
    background-image: linear-gradient(45deg, var(--bg-pattern-color) 25%, transparent 25%),
                      linear-gradient(-45deg, var(--bg-pattern-color) 25%, transparent 25%),
                      linear-gradient(45deg, transparent 75%, var(--bg-pattern-color) 75%),
                      linear-gradient(-45deg, transparent 75%, var(--bg-pattern-color) 75%);
    background-size: 20px 20px;
    transition: background-color 0.3s ease;
}

.container {
    text-align: center;
    background-color: var(--container-bg);
    padding: 40px;
    border-radius: 15px;
    box-shadow: 0 10px 20px var(--shadow-color), 0 6px 6px var(--shadow-color);
    transition: background-color 0.3s ease, box-shadow 0.3s ease;
    position: relative;
}

h1 {
    color: var(--text-color);
    font-size: 3em;
    margin-bottom: 20px;
    text-shadow: 1px 1px 2px rgba(0,0,0,0.1);
    transition: color 0.3s ease;
}

#theme-toggle {
    position: absolute;
    top: 10px;
    right: 10px;
    padding: 8px 12px;
    cursor: pointer;
    border: none;
    border-radius: 5px;
    background-color: var(--text-color);
    color: var(--container-bg);
    font-size: 0.9em;
    transition: all 0.3s ease;
}

#theme-toggle:hover {
    opacity: 0.8;
}

.contact-section {
    margin-top: 40px;
    padding-top: 20px;
    text-align: left;
}

.contact-section hr {
    border: 0;
    border-top: 1px solid var(--bg-pattern-color);
    margin-bottom: 20px;
}

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

.form-group {
    margin-bottom: 15px;
}

input[type="email"],
textarea {
    width: 100%;
    padding: 12px;
    border: 1px solid var(--bg-pattern-color);
    border-radius: 8px;
    background-color: var(--bg-color);
    color: var(--text-color);
    font-size: 1em;
    box-sizing: border-box;
    transition: all 0.3s ease;
}

textarea {
    height: 100px;
    resize: vertical;
}

input[type="email"]:focus,
textarea:focus {
    outline: none;
    border-color: var(--button-bg);
    box-shadow: 0 0 5px var(--button-bg);
}

.submit-btn {
    width: 100%;
    padding: 12px;
    background-color: var(--button-bg);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1.1em;
    cursor: pointer;
    transition: background-color 0.3s ease;
}

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