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

body {
    font-family: "Inter", Arial, sans-serif;
    background: #f5f7fa;
    color: #222;
    line-height: 1.6;
}

/* ----- HEADER ----- */
header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px;
    background: white;
    border-bottom: 1px solid #ddd;
    position: sticky;
    top: 0;
    z-index: 1000;
}

.logo {
    font-size: 24px;
    font-weight: 700;
    color: #333;
}

/* Desktop menu */
nav ul {
    display: flex;
    gap: 20px;
    list-style: none;
}

nav a {
    text-decoration: none;
    color: #333;
    font-weight: 500;
}

nav a:hover {
    color: #0078ff;
}

/* ----- HAMBURGER ----- */
.hamburger {
    display: none;
    flex-direction: column;
    gap: 4px;
    cursor: pointer;
}

.hamburger div {
    width: 25px;
    height: 3px;
    background: #333;
}

/* Mobile menu hidden by default */
.mobile-menu {
    display: none;
    flex-direction: column;
    background: white;
    padding: 20px;
    border-bottom: 1px solid #ddd;
}

.mobile-menu a {
    padding: 12px 0;
    font-size: 18px;
}

/* ----- CONTENT ----- */
.container {
    max-width: 900px;
    margin: 40px auto;
    padding: 20px;
    background: white;
    border-radius: 12px;
    border: 1px solid #ddd;
}

h1, h2, h3 {
    margin-bottom: 20px;
    font-weight: 700;
}

/* ----- FOOTER ----- */
footer {
    text-align: center;
    padding: 25px;
    margin-top: 40px;
    color: #666;
}

/* ----- RESPONSIVE ----- */
@media (max-width: 800px) {
    nav ul {
        display: none;
    }
    .hamburger {
        display: flex;
    }
}

/* ----- DARK MODE ----- */
body.dark {
    background: #111;
    color: #eee;
}

body.dark header,
body.dark .container,
body.dark .mobile-menu {
    background: #1a1a1a;
    color: #eee;
    border-color: #333;
}

body.dark a {
    color: #4da3ff;
}