.header {
    position: sticky;
    top: 0;
    background: var(--background);
    border-bottom: 1px solid var(--border);
    z-index: var(--z-sticky);
    transition: all var(--transition-base);
}

.header.scrolled {
    box-shadow: var(--shadow-md);
}

.nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 80px;
}

.nav-left {
    display: flex;
    align-items: center;
    gap: var(--spacing-xl);
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    text-decoration: none;
}

.logo-img {
    height: 40px;
    width: auto;
}

.logo-text {
    font-size: var(--font-size-xl);
    font-weight: 600;
    color: var(--text-primary);
}

.logo-text span {
    font-weight: 300;
    color: var(--text-secondary);
}

.nav-links {
    display: flex;
    gap: var(--spacing-lg);
}

.nav-link {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    position: relative;
    transition: color var(--transition-fast);
    padding: var(--spacing-xs) 0;
}

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

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 2px;
    background: var(--primary);
    border-radius: var(--radius-full);
}

.nav-right {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

.search-toggle {
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: var(--font-size-lg);
    cursor: pointer;
    padding: var(--spacing-sm);
    border-radius: var(--radius-full);
    transition: all var(--transition-fast);
}

.search-toggle:hover {
    color: var(--primary);
    background: var(--primary-soft);
}

.auth-buttons {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

.btn-login {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

.btn-login:hover {
    color: var(--primary);
    background: var(--primary-soft);
}

.btn-register {
    background: var(--primary);
    color: white;
    text-decoration: none;
    font-weight: 500;
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

.btn-register:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.btn-write {
    background: var(--primary-dark);
    color: white;
    text-decoration: none;
    font-weight: 500;
    padding: var(--spacing-sm) var(--spacing-lg);
    border-radius: var(--radius-full);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-left: var(--spacing-md);
    transition: all var(--transition-fast);
}

.btn-write i {
    font-size: var(--font-size-sm);
}

.btn-write:hover {
    background: var(--primary);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.mobile-menu-toggle {
    display: none;
    background: none;
    border: none;
    color: var(--text-primary);
    font-size: var(--font-size-xl);
    cursor: pointer;
    padding: var(--spacing-sm);
    border-radius: var(--radius-md);
}

.mobile-menu {
    display: none;
    position: fixed;
    top: 80px;
    left: 0;
    right: 0;
    background: var(--background);
    border-bottom: 1px solid var(--border);
    padding: var(--spacing-lg);
    z-index: var(--z-above);
    transform: translateY(-100%);
    transition: transform var(--transition-base);
    max-height: calc(100vh - 80px);
    overflow-y: auto;
}

.mobile-menu.active {
    transform: translateY(0);
}

.mobile-link {
    display: block;
    padding: var(--spacing-md);
    color: var(--text-primary);
    text-decoration: none;
    font-weight: 500;
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

.mobile-link:hover {
    background: var(--primary-soft);
    color: var(--primary);
}

.mobile-link.write-link {
    background: var(--primary);
    color: white;
    margin-top: var(--spacing-md);
}

.mobile-link.write-link:hover {
    background: var(--primary-dark);
}

.mobile-link.logout-link {
    color: var(--error);
}

.mobile-link.logout-link:hover {
    background: #FFEBEE;
}

.mobile-auth-divider {
    height: 1px;
    background: var(--border);
    margin: var(--spacing-md) 0;
}

.user-menu {
    position: relative;
}

.user-menu-toggle {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--spacing-sm);
    border-radius: var(--radius-full);
    transition: background var(--transition-fast);
}

.user-menu-toggle:hover {
    background: var(--primary-soft);
}

.user-avatar {
    width: 32px;
    height: 32px;
    border-radius: var(--radius-full);
    object-fit: cover;
}

.user-name {
    color: var(--text-primary);
    font-weight: 500;
}

.user-dropdown {
    position: absolute;
    top: 100%;
    right: 0;
    width: 220px;
    background: var(--background);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-xl);
    margin-top: var(--spacing-sm);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: all var(--transition-fast);
    z-index: var(--z-dropdown);
}

.user-dropdown.active {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.dropdown-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    padding: var(--spacing-md) var(--spacing-lg);
    color: var(--text-primary);
    text-decoration: none;
    transition: background var(--transition-fast);
}

.dropdown-item:hover {
    background: var(--primary-soft);
    color: var(--primary);
}

.dropdown-item.logout {
    color: var(--error);
}

.dropdown-item.logout:hover {
    background: #FFEBEE;
}

.dropdown-divider {
    height: 1px;
    background: var(--border);
    margin: var(--spacing-xs) 0;
}

.search-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.9);
    z-index: var(--z-modal);
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-base);
}

.search-overlay.active {
    opacity: 1;
    visibility: visible;
}

.search-overlay-content {
    width: 100%;
    max-width: 600px;
    padding: var(--spacing-lg);
    position: relative;
}

.search-overlay-form {
    display: flex;
    gap: var(--spacing-md);
}

.search-overlay-input {
    flex: 1;
    padding: var(--spacing-lg);
    font-size: var(--font-size-xl);
    border: none;
    border-radius: var(--radius-lg);
    background: var(--background);
    color: var(--text-primary);
}

.search-overlay-input:focus {
    outline: 2px solid var(--primary);
    box-shadow: none;
}

.search-overlay-submit {
    background: var(--primary);
    color: white;
    border: none;
    border-radius: var(--radius-lg);
    padding: 0 var(--spacing-xl);
    font-size: var(--font-size-lg);
    cursor: pointer;
    transition: background var(--transition-fast);
}

.search-overlay-submit:hover {
    background: var(--primary-dark);
}

.search-overlay-close {
    position: absolute;
    top: var(--spacing-lg);
    right: var(--spacing-lg);
    background: none;
    border: none;
    color: white;
    font-size: var(--font-size-2xl);
    cursor: pointer;
    opacity: 0.8;
    transition: opacity var(--transition-fast);
}

.search-overlay-close:hover {
    opacity: 1;
}

@media (max-width: 1024px) {
    .nav-links {
        display: none;
    }

    .auth-buttons {
        gap: var(--spacing-xs);
    }

    .btn-login,
    .btn-register {
        padding: var(--spacing-xs) var(--spacing-sm);
        font-size: var(--font-size-sm);
    }

    .btn-write {
        padding: var(--spacing-xs) var(--spacing-md);
        margin-left: 0;
        font-size: var(--font-size-sm);
    }

    .btn-write i {
        margin-right: 0;
    }

    .mobile-menu-toggle {
        display: block;
    }

    .mobile-menu {
        display: block;
    }

    .user-name {
        display: none;
    }
}

@media (max-width: 768px) {
    .nav {
        height: 70px;
    }

    .logo-text {
        display: none;
    }

    .btn-login,
    .btn-register {
        display: none;
    }

    .btn-write {
        padding: var(--spacing-xs) var(--spacing-sm);
    }

    .btn-write i {
        font-size: var(--font-size-md);
    }

    .btn-write span {
        display: none;
    }
}

@media (max-width: 480px) {
    .search-overlay-input {
        font-size: var(--font-size-md);
        padding: var(--spacing-md);
    }

    .search-overlay-submit {
        padding: 0 var(--spacing-lg);
    }

    .user-avatar {
        width: 28px;
        height: 28px;
    }
}