:root {
    --bg-color: #f9f9f9;
    --text-color: #333;
    --card-bg-color: #ffffff;
    --card-shadow: 0 10px 20px rgba(0,0,0,0.1);
    --hero-bg-color: rgba(0, 0, 0, 0.5);
    --hero-text-color: #ffffff;
    --button-bg-color: #007bff;
    --button-text-color: #ffffff;
    --footer-bg-color: #333;
    --footer-text-color: #f2f2f2;
}

[data-theme='dark'] {
    --bg-color: #1a1a1a;
    --text-color: #f2f2f2;
    --card-bg-color: #2c2c2c;
    --card-shadow: 0 10px 20px rgba(0,0,0,0.3);
    --hero-bg-color: rgba(0, 0, 0, 0.7);
    --button-bg-color: #0056b3;
}

body {
    font-family: 'Helvetica Neue', Arial, sans-serif;
    margin: 0;
    background-color: var(--bg-color);
    color: var(--text-color);
    transition: background-color 0.3s, color 0.3s;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 50px;
    background-color: var(--card-bg-color);
    box-shadow: var(--card-shadow);
}

header h1 {
    margin: 0;
}

header nav ul {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
}

header nav li {
    margin-left: 30px;
}

header nav a {
    text-decoration: none;
    color: var(--text-color);
    font-weight: bold;
}

#theme-toggle {
    background: none;
    border: none;
    color: var(--text-color);
    cursor: pointer;
    font-size: 1.2rem;
    margin-left: 20px;
}

main {
    padding: 20px 50px;
}

#hero {
    background-image: url('https://images.unsplash.com/photo-1507525428034-b723a9ce6890?q=80&w=2070&auto=format&fit=crop');
    background-size: cover;
    background-position: center;
    height: 60vh;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    color: var(--hero-text-color);
    position: relative;
}

#hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: var(--hero-bg-color);
}

.hero-text {
    position: relative;
    z-index: 1;
}

.hero-text h2 {
    font-size: 3rem;
    margin: 0;
}

#techniques h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 40px;
}

.technique-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
}

.card {
    background-color: var(--card-bg-color);
    border-radius: 15px;
    overflow: hidden;
    box-shadow: var(--card-shadow);
    transition: transform 0.3s, box-shadow 0.3s;
}

.card:hover {
    transform: translateY(-10px);
    box-shadow: 0 20px 40px rgba(0,0,0,0.2);
}

.card img {
    width: 100%;
    height: 200px;
    object-fit: cover;
}

.card h3 {
    padding: 20px 20px 10px;
    margin: 0;
}

.card p {
    padding: 0 20px 20px;
    margin: 0;
    line-height: 1.6;
}

#mailing-list {
    text-align: center;
    padding: 50px 20px;
    margin-top: 50px;
    background-color: var(--card-bg-color);
    box-shadow: var(--card-shadow);
    border-radius: 15px;
}

#mailing-list h2 {
    font-size: 2rem;
    margin-bottom: 20px;
}

#mailing-list form {
    display: flex;
    justify-content: center;
    align-items: center;
}

#mailing-list input {
    padding: 10px;
    font-size: 1rem;
    border: 1px solid #ccc;
    border-radius: 5px;
    width: 300px;
    margin-right: 10px;
}

#mailing-list button {
    padding: 10px 20px;
    font-size: 1rem;
    border: none;
    background-color: var(--button-bg-color);
    color: var(--button-text-color);
    border-radius: 5px;
    cursor: pointer;
}

footer {
    background-color: var(--footer-bg-color);
    color: var(--footer-text-color);
    text-align: center;
    padding: 20px;
    margin-top: 50px;
}

@media (max-width: 768px) {
    header {
        flex-direction: column;
        padding: 20px;
    }

    header nav ul {
        margin-top: 20px;
        flex-direction: column;
        align-items: center;
    }

    header nav li {
        margin: 10px 0;
    }

    main {
        padding: 20px;
    }
}