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

html {
    scroll-behavior: smooth;
}

body {
    font-family: Arial, sans-serif;
    background: #f5f7fb;
    color: #222;
    line-height: 1.7;
    transition: background 0.3s, color 0.3s;
}

.container {
    width: 90%;
    max-width: 1100px;
    margin: auto;
}

header {
    background: white;
    box-shadow: 0 2px 10px #00000012;
    padding: 18px 0;
}

.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 20px;
}

.logo {
    color: #0757d5;
    font-size: 26px;
}

nav {
    display: flex;
    gap: 20px;
    flex-wrap: wrap;
}

nav a {
    color: #222;
    text-decoration: none;
    font-weight: bold;
}

nav a:hover {
    color: #0757d5;
}

button,
.btn {
    cursor: pointer;
}

#themeBtn {
    border: none;
    background: #e8efff;
    padding: 10px;
    border-radius: 8px;
    font-size: 18px;
}

.hero {
    background: linear-gradient(135deg, #0757d5, #5925c7);
    color: white;
    text-align: center;
    padding: 100px 20px;
}

.hero h2 {
    font-size: 42px;
    margin-bottom: 15px;
}

.hero p {
    font-size: 18px;
    margin-bottom: 25px;
}

.btn {
    display: inline-block;
    background: #0757d5;
    color: white;
    padding: 12px 25px;
    border: none;
    border-radius: 6px;
    text-decoration: none;
    font-size: 16px;
}

.hero .btn {
    background: white;
    color: #0757d5;
}

.btn:hover {
    opacity: 0.85;
}

.section {
    padding: 65px 0;
    text-align: center;
}

.section h2 {
    margin-bottom: 20px;
    font-size: 30px;
}

.services {
    background: white;
}

.cards {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 20px;
    margin-top: 30px;
}

.card {
    background: #f5f7fb;
    padding: 30px 20px;
    border-radius: 10px;
    border: 1px solid #e0e6f0;
}

.card h3 {
    color: #0757d5;
    margin-bottom: 10px;
}

#contactForm {
    max-width: 550px;
    margin: 25px auto 0;
    display: flex;
    flex-direction: column;
    gap: 15px;
}

input,
textarea {
    width: 100%;
    padding: 14px;
    border: 1px solid #ccc;
    border-radius: 6px;
    font: inherit;
}

textarea {
    min-height: 130px;
    resize: vertical;
}

#formResult {
    margin-top: 15px;
}

footer {
    background: #111827;
    color: white;
    text-align: center;
    padding: 22px;
}

/* Dark Mode */
body.dark {
    background: #111827;
    color: #f5f5f5;
}

body.dark header,
body.dark .services {
    background: #1f2937;
}

body.dark nav a {
    color: white;
}

body.dark .card {
    background: #273449;
    border-color: #374151;
}

body.dark input,
body.dark textarea {
    background: #1f2937;
    color: white;
    border-color: #4b5563;
}

body.dark #themeBtn {
    background: #374151;
    color: white;
}

/* Mobile Design */
@media (max-width: 768px) {
    .navbar {
        flex-direction: column;
    }

    nav {
        justify-content: center;
        gap: 12px;
    }

    .hero {
        padding: 70px 15px;
    }

    .hero h2 {
        font-size: 30px;
    }

    .cards {
        grid-template-columns: 1fr;
    }

    .section {
        padding: 45px 0;
    }
}
```