/* ============================================
   HEADER.CSS — Navigation & Header
   ============================================ */

header {
    position: fixed;
    top: 0;
    width: 100%;
    height: var(--header-height);
    background-color: rgba(255, 255, 255, 0.85);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    z-index: 1000;
    box-shadow: 0 1px 0 var(--border-color);
    transition: background-color 0.3s;
}

body.dark-mode header {
    background-color: rgba(17, 24, 39, 0.85);
    box-shadow: 0 1px 0 var(--border-color);
}

.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 2rem;
    height: 100%;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-color);
}

.logo .highlight { color: var(--primary-color); }

.nav-links {
    display: flex;
    gap: 2rem;
}

.nav-links a {
    font-weight: 500;
    color: var(--text-color);
    position: relative;
}

.nav-links a:hover,
.nav-links a.active {
    color: var(--primary-color);
}

.nav-links a::after {
    content: '';
    position: absolute;
    width: 0;
    height: 2px;
    bottom: -4px;
    left: 0;
    background-color: var(--primary-color);
    transition: width 0.3s ease;
}

.nav-links a:hover::after,
.nav-links a.active::after {
    width: 100%;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 1rem;
}

#theme-toggle {
    background: none;
    border: none;
    cursor: pointer;
    font-size: 1.2rem;
    color: var(--text-color);
    padding: 0.5rem;
    border-radius: 50%;
    transition: background-color 0.3s;
}

#theme-toggle:hover { background-color: var(--border-color); }

/* ---- Mobile Hamburger ---- */
.hamburger {
    display: none;
    cursor: pointer;
    flex-direction: column;
    gap: 5px;
}

.hamburger .line {
    width: 25px;
    height: 3px;
    background-color: var(--text-color);
    border-radius: 2px;
    transition: all 0.3s ease;
}

.hamburger.active .line:nth-child(1) {
    transform: translateY(8px) rotate(45deg);
}

.hamburger.active .line:nth-child(2) { opacity: 0; }

.hamburger.active .line:nth-child(3) {
    transform: translateY(-8px) rotate(-45deg);
}