:root {
    --primary-color: #3b82f6;
    --secondary-color: #10b981;
    --background-color: #ffffff;
    --text-color: #1f2937;
    --container-bg: #f9fafb;
    --border-color: #e5e7eb;
    --shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

html.dark-mode {
    --primary-color: #60a5fa;
    --secondary-color: #34d399;
    --background-color: #111827;
    --text-color: #f9fafb;
    --container-bg: #1f2937;
    --border-color: #374151;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Roboto', sans-serif;
    line-height: 1.6;
    background-color: var(--background-color);
    color: var(--text-color);
    transition: background-color 0.3s, color 0.3s;
}

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 20px;
}

.header {
    background-color: var(--container-bg);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 10;
}

.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.5rem;
    font-weight: bold;
    text-decoration: none;
    color: var(--text-color);
}

.nav-menu {
    display: flex;
    align-items: center;
    list-style: none;
    gap: 1.5rem;
}

.nav-menu a {
    text-decoration: none;
    color: var(--text-color);
    font-weight: bold;
    transition: color 0.3s;
}

.nav-menu a:hover {
    color: var(--primary-color);
}

.btn {
    padding: 0.6rem 1.2rem;
    border-radius: 5px;
    text-decoration: none;
    font-weight: bold;
    transition: opacity 0.3s;
}

.btn-primary {
    background-color: var(--primary-color);
    color: #fff;
}

.btn-secondary {
    background-color: var(--secondary-color);
    color: #fff;
}

.btn:hover {
    opacity: 0.9;
}

.theme-toggle, .hamburger {
    background: none;
    border: none;
    color: var(--text-color);
    cursor: pointer;
    font-size: 1.5rem;
}

.hamburger {
    display: none;
    flex-direction: column;
    gap: 4px;
}

.hamburger span {
    display: block;
    width: 25px;
    height: 3px;
    background-color: var(--text-color);
}

.hero {
    text-align: center;
    padding: 6rem 0;
    background-color: var(--container-bg);
}

.hero h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.hero .subtitle {
    font-size: 1.25rem;
    margin-bottom: 2rem;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.how-it-works {
    padding: 4rem 0;
    text-align: center;
}

.how-it-works h2 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.cards-container {
    display: flex;
    justify-content: center;
    gap: 2rem;
    margin-top: 3rem;
    flex-wrap: wrap;
}

.card {
    background-color: var(--container-bg);
    padding: 2rem;
    border-radius: 8px;
    box-shadow: var(--shadow);
    flex: 1;
    max-width: 350px;
    transition: transform 0.3s, box-shadow 0.3s;
}

.card:hover {
    transform: translateY(-10px);
    box-shadow: 0 8px 15px rgba(0, 0, 0, 0.15);
}

.card h3 {
    margin-bottom: 1rem;
    color: var(--primary-color);
}

.footer {
    text-align: center;
    padding: 2rem 0;
    background-color: var(--container-bg);
    border-top: 1px solid var(--border-color);
}

@media (max-width: 768px) {
    .hamburger {
        display: flex;
    }

    .nav-menu {
        display: none;
        flex-direction: column;
        background-color: var(--container-bg);
        position: absolute;
        top: 60px;
        left: 0;
        width: 100%;
        padding: 1rem 0;
        border-bottom: 1px solid var(--border-color);
    }

    .nav-menu.active {
        display: flex;
    }

    .hero h1 {
        font-size: 2.5rem;
    }
}