.app-container {
    display: flex;
    height: 100vh;
    width: 100vw;
    position: relative;
    overflow: hidden;
}

/* --- MOBILE HEADER --- */
.mobile-header {
    display: none;
    align-items: center;
    justify-content: space-between;
    height: 64px;
    padding: 0 16px;
    background-color: var(--c-bg-sidebar);
    border-bottom: 1px solid var(--c-border-subtle);
    z-index: 20;
}

.mobile-header .logo-container {
    margin: 0;
}

.sidebar-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.6);
    backdrop-filter: blur(4px);
    z-index: 90;
    opacity: 0;
    transition: opacity var(--transition-smooth);
}

/* --- SIDEBAR --- */
.sidebar {
    width: var(--sidebar-width);
    background-color: var(--c-bg-sidebar);
    border-right: 1px solid var(--c-border-subtle);
    display: flex;
    flex-direction: column;
    z-index: 100;
    transition: transform var(--transition-smooth);
}

.sidebar-header {
    padding: 24px;
}

.logo-container {
    display: flex;
    align-items: center;
    gap: 12px;
}

.logo-container .logo-image {
    width: 32px;
    height: 32px;
    object-fit: contain;
    display: block;
    border: none;
    background: none;
    box-shadow: none;
}

.logo-container h1 {
    font-size: 1.1rem;
    font-weight: 600;
    letter-spacing: -0.03em;
    color: var(--c-text-primary);
}

.nav-tree {
    flex: 1;
    overflow-y: auto;
    padding: 16px 12px;
    position: relative;
}

/* ПРОФЕССИОНАЛЬНЫЙ ИНДИКАТОР */
.nav-indicator {
    position: absolute;
    top: 0; /* ИСПРАВЛЕНИЕ: Жесткая привязка к верху, исключает баг смещения от padding */
    left: 4px;
    width: 4px;
    border-radius: 9999px;
    background-color: var(--c-accent-primary);
    box-shadow: 0 0 10px var(--c-accent-glow);
    opacity: 0;
    transition: opacity var(--transition-fast);
    pointer-events: none;
    z-index: 2;
}

.nav-category {
    margin-bottom: 24px;
}

.nav-category-title {
    padding: 0 12px;
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    font-weight: 600;
    color: var(--c-text-muted);
    margin-bottom: 8px;
}

.nav-item {
    padding: 8px 12px;
    margin-bottom: 2px;
    cursor: pointer;
    color: var(--c-text-secondary);
    font-size: 0.9rem;
    font-weight: 500;
    border-radius: 6px;
    transition: var(--transition-fast);
    display: flex;
    align-items: center;
    position: relative;
}

.nav-item:hover {
    background-color: var(--c-border-subtle);
    color: var(--c-text-primary);
}

.nav-item.active {
    background-color: var(--c-bg-surface);
    color: var(--c-text-primary);
}

.sidebar-footer {
    padding: 16px;
    border-top: 1px solid var(--c-border-subtle);
}

/* --- MAIN CONTENT AREA --- */
.content-area {
    flex: 1;
    overflow-y: auto;
    background: var(--c-bg-base);
    position: relative;
    padding: 4rem 2rem 8rem 2rem;
    scroll-behavior: smooth;
}

/* УЛЬТРА-ПРЕМИАЛЬНОЕ СВЕЧЕНИЕ НА ФОНЕ */
.content-area::before {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 70vh;
    min-height: 500px;
    background: 
        radial-gradient(ellipse at 15% 0%, rgba(107, 33, 168, 0.25) 0%, transparent 55%),
        radial-gradient(ellipse at 85% 0%, rgba(88, 28, 135, 0.25) 0%, transparent 55%),
        radial-gradient(ellipse at 50% -10%, rgba(124, 58, 237, 0.15) 0%, transparent 65%);
    filter: blur(60px);
    pointer-events: none;
    z-index: 0;
    transform: translateZ(0); /* Аппаратное ускорение для плавности */
}

.content-transition-wrapper {
    position: relative; /* Выносит контент поверх свечения */
    z-index: 1;
    transition: opacity 0.25s ease, transform 0.25s ease;
    opacity: 1;
    transform: translateY(0);
}

.content-transition-wrapper.fading {
    opacity: 0;
    transform: translateY(10px);
}

/* --- BOTTOM NAVIGATION (Next/Prev) --- */
.doc-navigation {
    max-width: var(--content-text-width);
    margin: 4rem auto 0 auto;
    display: flex;
    gap: 1.5rem;
    border-top: 1px solid var(--c-border-subtle);
    padding-top: 2rem;
}

.nav-card {
    flex: 1;
    display: flex;
    flex-direction: column;
    padding: 20px 24px;
    border-radius: 12px;
    background: var(--c-bg-surface);
    border: 1px solid var(--c-border-strong);
    text-decoration: none;
    transition: all var(--transition-fast);
    cursor: pointer;
}

.nav-card:hover {
    background: #111111;
    border-color: var(--c-text-muted);
}

.nav-card.prev { align-items: flex-start; text-align: left; }
.nav-card.next { align-items: flex-end; text-align: right; }

.nav-card-label {
    font-size: 0.8rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--c-text-muted);
    margin-bottom: 8px;
    font-weight: 600;
}

.nav-card-title {
    font-size: 1.1rem;
    color: var(--c-text-primary);
    font-weight: 500;
}

.nav-card.empty {
    visibility: hidden;
    pointer-events: none;
}

/* --- BUTTONS --- */
.btn-primary {
    background-color: var(--c-text-primary);
    color: var(--c-bg-base);
    border: none;
    padding: 8px 16px;
    border-radius: 6px;
    font-weight: 600;
    font-size: 0.9rem;
    cursor: pointer;
    transition: var(--transition-fast);
    display: inline-flex;
    align-items: center;
    gap: 8px;
}

.btn-primary:hover {
    background-color: #D4D4D8; 
}

.btn-ghost {
    background-color: transparent;
    color: var(--c-text-secondary);
    border: 1px solid var(--c-border-strong);
    padding: 8px 16px;
    border-radius: 6px;
    font-weight: 500;
    font-size: 0.9rem;
    cursor: pointer;
    transition: var(--transition-fast);
    display: inline-flex;
    align-items: center;
    gap: 8px;
}

.btn-ghost:hover {
    background-color: var(--c-bg-surface);
    color: var(--c-text-primary);
}

.btn-icon {
    background: transparent;
    border: none;
    color: var(--c-text-secondary);
    cursor: pointer;
    padding: 8px;
    border-radius: 6px;
    transition: var(--transition-fast);
    display: grid;
    place-items: center;
}

.btn-icon:hover {
    background-color: var(--c-bg-surface);
    color: var(--c-text-primary);
}

.nav-action-btn {
    width: 100%;
    background: transparent;
    border: 1px solid var(--c-border-subtle);
    color: var(--c-text-secondary);
    padding: 10px 12px;
    border-radius: 6px;
    cursor: pointer;
    transition: var(--transition-fast);
    display: flex;
    align-items: center;
    gap: 12px;
    font-size: 0.9rem;
    font-weight: 500;
}

.nav-action-btn:hover {
    background: var(--c-bg-surface);
    color: var(--c-text-primary);
    border-color: var(--c-border-strong);
}

.loading-state {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 40vh;
    color: var(--c-text-muted);
}
.spinner {
    animation: spin 1s linear infinite;
    font-size: 24px;
    margin-bottom: 16px;
    color: var(--c-text-secondary);
}
@keyframes spin { 100% { transform: rotate(360deg); } }

/* =========================================
   MOBILE ADAPTATION (Phones & Small Tablets)
   ========================================= */
@media (max-width: 768px) {
    .app-container {
        flex-direction: column;
    }
    
    .mobile-header {
        display: flex;
    }

    .sidebar {
        position: fixed;
        top: 0;
        left: 0;
        height: 100%;
        transform: translateX(-100%);
        background-color: var(--c-bg-base);
    }
    
    .sidebar.open {
        transform: translateX(0);
    }

    .sidebar-overlay.active {
        display: block;
        opacity: 1;
    }

    .content-area {
        padding: 2rem 1.5rem 6rem 1.5rem;
    }

    .doc-navigation {
        flex-direction: column;
        gap: 1rem;
    }
}