/* ==========================================
   TopBar / Navigation
   ========================================== */

.topbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--topbar-height);
    background-color: transparent;
    z-index: var(--z-sticky);
    transition: background-color var(--transition-normal), box-shadow var(--transition-normal);
}

/* Filled TopBar - Projects 섹션부터 적용 */
.topbar.filled {
    background-color: var(--color-sf-00);
    box-shadow: 0 1px 0 var(--color-sf-01);
}

.topbar-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 100%;
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 16px 24px;
    gap: 24px;
}

/* Logo */
.logo {
    color: #f6f6f7; /* About Hero에서는 밝은 텍스트 (하드코딩) */
    font-size: 16px;
    font-family: 'The Bold Font', sans-serif;
    font-weight: 700;
    letter-spacing: -2%;
    transition: opacity var(--transition-fast), color var(--transition-normal);
}

.topbar.filled .logo {
    color: var(--color-obj-00); /* Filled 상태에서는 CSS Variable 사용 */
}

.logo:hover {
    opacity: 0.7;
}

/* Navigation */
.nav {
    display: flex;
    align-items: center;
    gap: 24px;
}

.nav-link {
    color: #f6f6f7; /* About Hero에서는 밝은 텍스트 (하드코딩) */
    font-size: 16px;
    font-family: 'The Bold Font', sans-serif;
    font-weight: 700;
    letter-spacing: -2%;
    transition: opacity var(--transition-fast), color var(--transition-normal);
    padding: 8px 8px 4px 8px;
}

.topbar.filled .nav-link {
    color: var(--color-obj); /* Filled 상태에서는 CSS Variable 사용 */
}

.nav-link:hover {
    opacity: 0.7;
}

/* Contact CTA Button */
.nav-link-cta {
    background-color: transparent;
    color: #ffffff; /* About Hero에서는 흰색 텍스트 (하드코딩) */
    padding: 8px 12px 4px 12px;
    border-radius: 8px;
    transition: none; /* Disable all transitions from .nav-link */
    position: relative;
    z-index: 0;
    opacity: 1; /* Override .nav-link opacity */
}

.topbar.filled .nav-link-cta {
    color: var(--color-sf-00);
}

/* Override .nav-link:hover opacity */
.nav-link-cta:hover {
    opacity: 1;
}

/* Glow effect for CTA button */
.nav-link-cta:before {
    content: '';
    background: linear-gradient(45deg, #ff0000, #ff7300, #fffb00, #48ff00, #00ffd5, #002bff, #7a00ff, #ff00c8, #ff0000);
    position: absolute;
    top: -2px;
    left: -2px;
    background-size: 400%;
    z-index: -1;
    filter: blur(5px);
    width: calc(100% + 4px);
    height: calc(100% + 4px);
    animation: glowing 20s linear infinite;
    opacity: 0;
    transition: opacity .3s ease-in-out;
    border-radius: 8px;
}

.nav-link-cta:hover:before {
    opacity: 1;
}

.nav-link-cta:after {
    z-index: -1;
    content: '';
    position: absolute;
    width: 100%;
    height: 100%;
    left: 0;
    top: 0;
    border-radius: 8px;
    background: rgba(255, 255, 255, 0.2);
    transition: background-color var(--transition-normal);
}

/* Blank state hover: black background */
.topbar:not(.filled) .nav-link-cta:hover:after {
    background: #000000;
}

/* Filled state: solid background */
.topbar.filled .nav-link-cta:after {
    background: var(--color-obj-00);
}

/* Mobile Menu Toggle Button */
.menu-toggle {
    display: none;
    flex-direction: column;
    gap: 6px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
    z-index: calc(var(--z-sticky) + 2);
    position: relative;
}

.hamburger-line {
    width: 24px;
    height: 2px;
    background-color: #f6f6f7;
    transition: background-color var(--transition-normal);
}

.topbar.filled .hamburger-line {
    background-color: var(--color-obj-00);
}

/* Mobile Sidebar */
.mobile-sidebar {
    position: fixed;
    top: 0;
    right: -100%;
    width: auto;
    min-width: 160px;
    height: 100vh;
    background-color: var(--color-sf-00);
    z-index: calc(var(--z-sticky) + 2);
    transition: right 0.3s ease-in-out;
    padding: 16px 24px;
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.mobile-sidebar.active {
    right: 0;
}

/* Sidebar Close Button */
.sidebar-close {
    display: flex;
    align-items: center;
    justify-content: center;
    background: none;
    border: none;
    cursor: pointer;
    padding: 0;
    width: 32px;
    height: 32px;
    align-self: flex-end;
    color: var(--color-obj-00);
    transition: opacity var(--transition-fast);
}

.sidebar-close:hover {
    opacity: 0.7;
}

.mobile-nav {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.mobile-nav-link {
    color: var(--color-obj-00);
    font-size: 16px;
    font-family: 'The Bold Font', sans-serif;
    font-weight: 700;
    letter-spacing: -2%;
    padding: 8px 8px 4px 8px;
    transition: opacity var(--transition-fast);
    white-space: nowrap;
}

.mobile-nav-link:hover {
    opacity: 0.7;
}

/* Mobile CTA Button */
.mobile-nav-link-cta {
    background-color: var(--color-obj-00);
    color: var(--color-sf-00);
    border-radius: 8px;
    padding: 8px 12px 4px 12px;
    position: relative;
    z-index: 0;
}

.mobile-nav-link-cta:hover {
    /* glow effect only, no other changes */
}

/* Glow effect for mobile CTA */
.mobile-nav-link-cta:before {
    content: '';
    background: linear-gradient(45deg, #ff0000, #ff7300, #fffb00, #48ff00, #00ffd5, #002bff, #7a00ff, #ff00c8, #ff0000);
    position: absolute;
    top: -2px;
    left: -2px;
    background-size: 400%;
    z-index: -1;
    filter: blur(5px);
    width: calc(100% + 4px);
    height: calc(100% + 4px);
    animation: glowing 20s linear infinite;
    opacity: 0;
    transition: opacity .3s ease-in-out;
    border-radius: 8px;
}

.mobile-nav-link-cta:hover:before {
    opacity: 1;
}

.mobile-nav-link-cta:after {
    z-index: -1;
    content: '';
    position: absolute;
    width: 100%;
    height: 100%;
    background: var(--color-obj-00);
    left: 0;
    top: 0;
    border-radius: 8px;
}

/* Sidebar Overlay */
.sidebar-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100vh;
    background-color: rgba(0, 0, 0, 0.2);
    opacity: 0;
    visibility: hidden;
    z-index: calc(var(--z-sticky) + 1);
    transition: opacity 0.3s ease-in-out, visibility 0.3s ease-in-out;
}

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

/* Responsive */
@media (max-width: 768px) {
    .topbar-content {
        padding: 16px 16px;
    }

    /* Hide desktop nav, show mobile toggle */
    .nav-desktop {
        display: none;
    }

    .menu-toggle {
        display: flex;
    }
}