/* Smooth Scroll Behavior */
html {
    scroll-behavior: smooth;
}

/* Adjust scroll position for sticky nav (scroll-margin-top) */
section[id],
header[id] {
    scroll-margin-top: 80px;
}

/* Skip Link (accessibility) */
.skip-link {
    position: absolute;
    top: -40px;
    left: 0;
    background-color: var(--color-primary);
    color: white;
    padding: var(--spacing-sm) var(--spacing-md);
    text-decoration: none;
    z-index: 1001;
    font-weight: var(--font-weight-medium);
}

.skip-link:focus {
    top: 0;
}

/* Navigation Sticky Header */
.nav {
    position: sticky;
    top: 0;
    z-index: 100;
    background-color: var(--color-background);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    transition: box-shadow var(--transition-default);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-md);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

/* Brand/Logo */
.nav-brand {
    font-size: 1.5rem;
    font-weight: var(--font-weight-bold);
    color: var(--color-text);
    text-decoration: none;
    transition: color var(--transition-default);
}

.nav-brand:hover,
.nav-brand:focus-visible {
    color: var(--color-primary);
}

.nav-brand:focus-visible {
    outline: 3px solid var(--color-primary);
    outline-offset: 4px;
}

/* Navigation Menu (mobile hidden by default) */
.nav-menu {
    display: none;
    list-style: none;
    margin: 0;
    padding: 0;
}

.nav-item {
    margin: 0;
}

.nav-link {
    display: block;
    padding: var(--spacing-md);
    font-size: var(--font-size-body);
    font-weight: var(--font-weight-medium);
    color: var(--color-text);
    text-decoration: none;
    transition: color var(--transition-default);
    border-bottom: 3px solid transparent;
}

.nav-link:hover,
.nav-link:focus-visible {
    color: var(--color-primary);
}

.nav-link.active {
    color: var(--color-primary);
    border-bottom-color: var(--color-primary);
}

.nav-link:focus-visible {
    outline: 3px solid var(--color-primary);
    outline-offset: 2px;
}

/* Burger Menu Button (mobile only) */
.nav-toggle {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    width: 40px;
    height: 40px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 0;
    z-index: 101;
}

.nav-toggle:focus-visible {
    outline: 3px solid var(--color-primary);
    outline-offset: 2px;
}

.burger-icon {
    position: relative;
    width: 30px;
    height: 3px;
    background-color: var(--color-text);
    transition: all var(--transition-default);
}

.burger-icon::before,
.burger-icon::after {
    content: '';
    position: absolute;
    width: 30px;
    height: 3px;
    background-color: var(--color-text);
    transition: all var(--transition-default);
}

.burger-icon::before {
    top: -10px;
}

.burger-icon::after {
    top: 10px;
}

/* Burger Icon Animation (when menu open) */
.nav-toggle.active .burger-icon {
    background-color: transparent;
}

.nav-toggle.active .burger-icon::before {
    top: 0;
    transform: rotate(45deg);
}

.nav-toggle.active .burger-icon::after {
    top: 0;
    transform: rotate(-45deg);
}

/* Mobile Menu Open State */
.nav-menu.open {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background-color: var(--color-background);
    box-shadow: 0 8px 16px rgba(0, 0, 0, 0.1);
    padding: var(--spacing-md) 0;
}

/* Tablet and Desktop (≥768px) */
@media (min-width: 768px) {
    /* Hide burger menu button */
    .nav-toggle {
        display: none;
    }
    
    /* Show navigation menu horizontally */
    .nav-menu {
        display: flex;
        flex-direction: row;
        gap: var(--spacing-md);
    }
    
    .nav-link {
        padding: var(--spacing-sm) var(--spacing-md);
    }
}

/* Desktop larger spacing (≥1024px) */
@media (min-width: 1024px) {
    .nav-menu {
        gap: var(--spacing-lg);
    }
}