/* ============================================
   LUNA WHALE ART LAB — Core Layout System v2
   통합 반응형 CSS (mobile / tablet / desktop)
   ============================================ */

/* ─── Design Tokens ─── */
:root {
    /* Layout dimensions */
    --sidebar-w: 240px;
    --mobile-nav-h: 64px;
    --header-h: 56px;
    --drawer-w: 280px;

    /* Breakpoints (for reference, used in @media) */
    /* mobile: ~639px */
    /* tablet: 640~1023px */
    /* desktop: 1024px+ */

    /* Colors - Light mode (default) */
    --lc-bg: #f6f6f8;
    --lc-bg-card: #ffffff;
    --lc-bg-sidebar: #ffffff;
    --lc-bg-nav: rgba(255, 255, 255, 0.92);
    --lc-text: #1a1a2e;
    --lc-text-secondary: #64748b;
    --lc-text-muted: #94a3b8;
    --lc-border: rgba(0, 0, 0, 0.08);
    --lc-border-hover: rgba(0, 0, 0, 0.15);
    --lc-accent: #6366f1;
    --lc-accent-light: rgba(99, 102, 241, 0.1);
    --lc-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
    --lc-shadow-lg: 0 8px 30px rgba(0, 0, 0, 0.08);

    /* Spacing */
    --sp-xs: 4px;
    --sp-sm: 8px;
    --sp-md: 16px;
    --sp-lg: 24px;
    --sp-xl: 40px;

    /* Radii */
    --r-sm: 8px;
    --r-md: 14px;
    --r-lg: 20px;
    --r-xl: 28px;
    --r-full: 9999px;

    /* Transition */
    --t-fast: 0.15s ease;
    --t-md: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
    --t-slow: 0.4s cubic-bezier(0.4, 0, 0.2, 1);

    /* Safe area for notch/dynamic island */
    --safe-top: env(safe-area-inset-top, 0px);
    --safe-bottom: env(safe-area-inset-bottom, 0px);
}

/* Dark mode tokens */
html.dark {
    --lc-bg: #0f1219;
    --lc-bg-card: #1a1f2e;
    --lc-bg-sidebar: #141821;
    --lc-bg-nav: rgba(20, 24, 33, 0.95);
    --lc-text: #f0ede8;
    --lc-text-secondary: #9ba4b5;
    --lc-text-muted: #5a677d;
    --lc-border: rgba(255, 255, 255, 0.08);
    --lc-border-hover: rgba(255, 255, 255, 0.15);
    --lc-accent: #818cf8;
    --lc-accent-light: rgba(129, 140, 248, 0.12);
    --lc-shadow: 0 1px 3px rgba(0, 0, 0, 0.3);
    --lc-shadow-lg: 0 8px 30px rgba(0, 0, 0, 0.3);
}


/* ============================================
   LAYOUT SHELL
   ============================================ */

/* ─── App Shell ─── */
.lc-app {
    display: flex;
    min-height: 100vh;
    min-height: 100dvh;
    background: var(--lc-bg);
    color: var(--lc-text);
}

.lc-main {
    flex: 1;
    min-width: 0; /* prevent flex overflow */
    padding-bottom: calc(var(--mobile-nav-h) + var(--safe-bottom));
    transition: margin-left var(--t-md);
}


/* ============================================
   DESKTOP SIDEBAR (1024px+)
   ============================================ */
.lc-sidebar {
    display: none; /* hidden on mobile/tablet */
    position: fixed;
    top: 0;
    left: 0;
    width: var(--sidebar-w);
    height: 100vh;
    height: 100dvh;
    background: var(--lc-bg-sidebar);
    border-right: 1px solid var(--lc-border);
    z-index: 100;
    flex-direction: column;
    overflow-y: auto;
    overflow-x: hidden;
    -webkit-overflow-scrolling: touch;
}

.lc-sidebar-header {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 20px 20px 16px;
    border-bottom: 1px solid var(--lc-border);
    flex-shrink: 0;
}

.lc-sidebar-logo {
    width: 36px;
    height: 36px;
    border-radius: var(--r-sm);
    object-fit: contain;
}

.lc-sidebar-title {
    font-size: 16px;
    font-weight: 700;
    color: var(--lc-text);
}

.lc-sidebar-nav {
    flex: 1;
    padding: 12px 12px;
    display: flex;
    flex-direction: column;
    gap: 2px;
}

.lc-sidebar-divider {
    height: 1px;
    background: var(--lc-border);
    margin: 8px 8px;
}

.lc-nav-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 10px 12px;
    border-radius: var(--r-sm);
    color: var(--lc-text-secondary);
    font-size: 14px;
    font-weight: 500;
    text-decoration: none;
    transition: all var(--t-fast);
    cursor: pointer;
    border: 1px solid transparent;
    min-height: 42px;
}

.lc-nav-item:hover {
    background: var(--lc-accent-light);
    color: var(--lc-accent);
}

.lc-nav-item.active {
    background: var(--lc-accent-light);
    color: var(--lc-accent);
    font-weight: 600;
}

.lc-nav-item .icon {
    font-size: 20px;
    width: 24px;
    text-align: center;
    flex-shrink: 0;
}

.lc-nav-spacer {
    flex: 1;
}


/* ============================================
   TABLET DRAWER (640~1023px)
   ============================================ */
.lc-drawer-backdrop {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.5);
    z-index: 199;
    opacity: 0;
    transition: opacity var(--t-md);
}

.lc-drawer-backdrop.open {
    opacity: 1;
}

.lc-drawer {
    position: fixed;
    top: 0;
    left: 0;
    width: var(--drawer-w);
    height: 100vh;
    height: 100dvh;
    background: var(--lc-bg-sidebar);
    z-index: 200;
    transform: translateX(-100%);
    transition: transform var(--t-md);
    overflow-y: auto;
    -webkit-overflow-scrolling: touch;
    box-shadow: 4px 0 24px rgba(0, 0, 0, 0.15);
}

.lc-drawer.open {
    transform: translateX(0);
}


/* ============================================
   TABLET HEADER (640~1023px)
   ============================================ */
.lc-header {
    display: none; /* shown only on tablet */
    position: sticky;
    top: 0;
    height: var(--header-h);
    background: var(--lc-bg-nav);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--lc-border);
    z-index: 50;
    padding: 0 16px;
    align-items: center;
    justify-content: space-between;
}

.lc-hamburger {
    width: 40px;
    height: 40px;
    border-radius: var(--r-sm);
    border: none;
    background: transparent;
    cursor: pointer;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 5px;
    padding: 0;
}

.lc-hamburger span {
    display: block;
    width: 20px;
    height: 2px;
    background: var(--lc-text);
    border-radius: 2px;
    transition: all 0.3s ease;
}

.lc-header-logo {
    font-size: 16px;
    font-weight: 700;
    color: var(--lc-text);
}

.lc-header-actions {
    display: flex;
    align-items: center;
    gap: 8px;
}


/* ============================================
   MOBILE BOTTOM NAV (<640px)
   ============================================ */
.lc-bottom-nav {
    display: flex;
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    height: calc(var(--mobile-nav-h) + var(--safe-bottom));
    padding-bottom: var(--safe-bottom);
    background: var(--lc-bg-nav);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-top: 1px solid var(--lc-border);
    z-index: 100;
    align-items: center;
    justify-content: space-around;
}

.lc-bottom-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 2px;
    padding: 6px 0;
    color: var(--lc-text-muted);
    font-size: 10px;
    font-weight: 500;
    text-decoration: none;
    cursor: pointer;
    transition: color var(--t-fast);
    -webkit-tap-highlight-color: transparent;
    min-width: 48px;
    min-height: 48px;
}

.lc-bottom-item .icon {
    font-size: 24px;
}

.lc-bottom-item.active {
    color: var(--lc-accent);
}

.lc-bottom-item:active {
    transform: scale(0.92);
}

/* FAB (center action button) */
.lc-fab {
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: var(--lc-accent);
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
    border: none;
    cursor: pointer;
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.3);
    transition: transform var(--t-fast), box-shadow var(--t-fast);
    -webkit-tap-highlight-color: transparent;
}

.lc-fab:active {
    transform: scale(0.9);
}


/* ============================================
   QUICK ACCESS GRID (2x3 icon grid)
   ============================================ */
.lc-quick-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 12px;
    padding: 16px;
    max-width: 400px;
    margin: 0 auto;
}

.lc-quick-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 8px;
    padding: 16px 8px;
    border-radius: var(--r-md);
    background: var(--lc-bg-card);
    border: 1px solid var(--lc-border);
    cursor: pointer;
    text-decoration: none;
    transition: all var(--t-fast);
    -webkit-tap-highlight-color: transparent;
}

.lc-quick-item:hover {
    border-color: var(--lc-border-hover);
    box-shadow: var(--lc-shadow-lg);
    transform: translateY(-2px);
}

.lc-quick-item:active {
    transform: scale(0.96);
}

.lc-quick-icon {
    width: 48px;
    height: 48px;
    border-radius: var(--r-md);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
}

.lc-quick-label {
    font-size: 12px;
    font-weight: 600;
    color: var(--lc-text);
    text-align: center;
    line-height: 1.2;
}


/* ============================================
   MASONRY GRID (responsive)
   ============================================ */
.lc-masonry {
    columns: 2;
    column-gap: 12px;
    padding: 0 16px;
}

.lc-masonry-item {
    break-inside: avoid;
    margin-bottom: 12px;
    display: block;
}


/* ============================================
   SECTION HEADERS
   ============================================ */
.lc-section {
    padding: 24px 16px 8px;
}

.lc-section-title {
    font-size: 18px;
    font-weight: 700;
    color: var(--lc-text);
}

.lc-section-subtitle {
    font-size: 13px;
    color: var(--lc-text-muted);
    margin-top: 2px;
}

/* Collapsible sections */
.lc-section-toggle {
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.lc-section-toggle .chevron {
    transition: transform var(--t-fast);
    color: var(--lc-text-muted);
}

.lc-section-toggle.collapsed .chevron {
    transform: rotate(-90deg);
}

.lc-section-body {
    overflow: hidden;
    transition: max-height var(--t-md), opacity var(--t-md);
}

.lc-section-body.collapsed {
    max-height: 0 !important;
    opacity: 0;
}


/* ============================================
   SLIM HUB HEADER (for Math/TECH/Korean/EN hubs)
   No sidebar, just a compact top bar
   ============================================ */
.lc-hub-header {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 16px;
    position: sticky;
    top: 0;
    z-index: 50;
    background: inherit;
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    min-height: 52px;
}

.lc-hub-back {
    width: 36px;
    height: 36px;
    border-radius: var(--r-sm);
    border: 1px solid var(--lc-border);
    background: transparent;
    color: var(--lc-text-secondary);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: 20px;
    transition: all var(--t-fast);
    -webkit-tap-highlight-color: transparent;
}

.lc-hub-back:hover {
    background: var(--lc-accent-light);
    color: var(--lc-accent);
}

.lc-hub-title {
    font-size: 16px;
    font-weight: 700;
    flex: 1;
}

.lc-hub-home {
    width: 36px;
    height: 36px;
    border-radius: var(--r-sm);
    background: transparent;
    border: none;
    color: var(--lc-text-muted);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: 20px;
    transition: all var(--t-fast);
    -webkit-tap-highlight-color: transparent;
}

.lc-hub-home:hover {
    color: var(--lc-accent);
}


/* ============================================
   RESPONSIVE MEDIA QUERIES
   ============================================ */

/* ─── Tablet (640px ~ 1023px) ─── */
@media (min-width: 640px) {
    .lc-masonry {
        columns: 3;
    }

    .lc-bottom-nav {
        display: none;
    }

    .lc-header {
        display: flex;
    }

    .lc-main {
        padding-bottom: 0;
    }

    .lc-quick-grid {
        max-width: 480px;
        gap: 16px;
    }

    .lc-quick-item {
        padding: 20px 12px;
    }

    .lc-quick-icon {
        width: 56px;
        height: 56px;
        font-size: 28px;
    }

    .lc-quick-label {
        font-size: 13px;
    }
}

/* ─── Desktop (1024px+) ─── */
@media (min-width: 1024px) {
    .lc-sidebar {
        display: flex;
    }

    .lc-header {
        display: none;
    }

    .lc-bottom-nav {
        display: none;
    }

    .lc-main {
        margin-left: var(--sidebar-w);
        padding-bottom: 0;
    }

    .lc-masonry {
        columns: 4;
        column-gap: 16px;
        padding: 0 24px;
    }

    .lc-quick-grid {
        max-width: 540px;
    }
}

/* ─── Large Desktop (1280px+) ─── */
@media (min-width: 1280px) {
    .lc-masonry {
        columns: 5;
    }
}

/* ─── Touch-friendly targets ─── */
@media (pointer: coarse) {
    .lc-nav-item {
        min-height: 48px;
    }

    .lc-bottom-item {
        min-height: 48px;
    }
}


/* ============================================
   UTILITY CLASSES
   ============================================ */
.lc-hide-mobile { display: none; }
.lc-hide-desktop { display: block; }

@media (min-width: 640px) {
    .lc-hide-tablet-up { display: none !important; }
}

@media (min-width: 1024px) {
    .lc-hide-mobile { display: block; }
    .lc-hide-desktop { display: none; }
}

/* Smooth scrollbar */
.lc-app {
    scrollbar-width: thin;
    scrollbar-gutter: stable;
}

.lc-app::-webkit-scrollbar {
    width: 6px;
}

.lc-app::-webkit-scrollbar-track {
    background: transparent;
}

.lc-app::-webkit-scrollbar-thumb {
    background: var(--lc-border);
    border-radius: 3px;
}