.app-container {
    display: flex;
    min-height: 100vh;
    width: 100%;
}

.sidebar {
    width: var(--sidebar-width);
    background-color: var(--color-surface);
    border-right: 1px solid var(--color-border);
    padding: clamp(1rem, 3vw, 3rem);
    display: flex;
    flex-direction: column;
    flex-shrink: 0;
    position: sticky;
    top: 0;
    height: 100vh;
    overflow-y: auto;
    overflow-x: hidden;
    z-index: 100;
    transition:
        width var(--transition-normal),
        padding var(--transition-normal),
        transform var(--transition-normal);
}

.sidebar.sidebar-state-pending {
    transition: none !important;
}

.sidebar .brand-logo {
    font-size: clamp(1.125rem, 1.5vw, 1.4rem);
    font-weight: 700;
    color: var(--color-primary);
    letter-spacing: -0.02em;
    margin-bottom: clamp(1rem, 2vw, 2.5rem);
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
    line-height: 1.2;
    text-decoration: none;
}

.sidebar .brand-logo__image {
    display: block;
    width: auto;
    height: clamp(2.75rem, 7vw, 3.5rem);
    max-width: 100%;
    margin-bottom: 0.625rem;
    object-fit: contain;
}

.sidebar .brand-logo__text {
    display: block;
}

.nav-menu {
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.nav-btn {
    width: 100%;
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0.75rem;
    border-radius: 0.5rem;
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--color-text-muted);
    transition: all 0.2s ease;
}

.nav-btn:hover {
    color: var(--hover-on-surface, #ffffff);
    background-color: var(--hover-surface, #182059);
}

.nav-btn.active {
    background-color: var(--color-hover);
    color: var(--color-primary);
}

.nav-btn .chevron-icon {
    transition: transform 0.2s ease;
}

.nav-btn.active .chevron-icon {
    transform: rotate(90deg);
}

.sub-menu {
    margin-left: 0.75rem;
    margin-top: 0.25rem;
    padding-left: 0.75rem;
    border-left: 1px solid var(--color-border);
    display: flex;
    flex-direction: column;
    gap: 0.125rem;
    animation: slideDown var(--transition-fast) forwards;
    transform-origin: top;
}

@keyframes slideDown {
    from {
        opacity: 0;
        transform: scaleY(0.95);
    }
    to {
        opacity: 1;
        transform: scaleY(1);
    }
}

.sub-nav-btn {
    width: 100%;
    text-align: left;
    padding: 0.5rem 0.75rem;
    border-radius: 0.375rem;
    font-size: 0.8rem;
    color: var(--color-text-muted);
    transition: all 0.2s;
    text-decoration: none;
}

.sub-nav-btn:hover {
    color: var(--hover-on-surface, #ffffff);
    background-color: var(--hover-surface, #182059);
}

.sub-nav-btn.active-sub {
    background-color: var(--color-hover);
    color: var(--color-accent);
    font-weight: 600;
}

.nav-item--books .sub-menu {
    max-height: min(40vh, 18rem);
    overflow-y: auto;
    scrollbar-width: thin;
    scrollbar-color: var(--color-border) transparent;
}

.nav-item--books .sub-menu::-webkit-scrollbar {
    width: 4px;
}

.nav-item--books .sub-menu::-webkit-scrollbar-thumb {
    background-color: var(--color-border);
    border-radius: 4px;
}

.main-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    min-width: 0;
    min-height: 100vh;
}

.mobile-header {
    display: none;
    align-items: center;
    justify-content: space-between;
    gap: 0.5rem;
    min-height: var(--mobile-header-height);
    padding: 0.375rem var(--page-padding);
    background-color: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
    flex-shrink: 0;
}

.mobile-header .brand-logo {
    font-size: clamp(1rem, 3.5vw, 1.125rem);
    font-weight: 700;
    color: var(--color-primary);
    letter-spacing: -0.02em;
    margin: 0;
    line-height: 1.2;
}

.menu-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    min-width: 44px;
    min-height: 44px;
    color: var(--color-text-main);
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.375rem;
    margin: 0;
    line-height: 0;
}

.menu-toggle .icon {
    width: 1.375rem;
    height: 1.375rem;
}

.sidebar.sidebar-closed {
    width: 0 !important;
    padding-left: 0 !important;
    padding-right: 0 !important;
    border-right: none !important;
}
.sidebar.sidebar-open {
    width: var(--sidebar-width) !important;
}

@media (min-width: 1025px) {
    .sidebar,
    .sidebar.sidebar-closed,
    .sidebar.sidebar-open {
        width: var(--sidebar-width) !important;
        padding-left: clamp(1rem, 3vw, 3rem) !important;
        padding-right: clamp(1rem, 3vw, 3rem) !important;
        border-right: 1px solid var(--color-border) !important;
        transform: none !important;
    }
}

@media (max-width: 1024px) {
    .sidebar {
        position: fixed;
        top: var(--mobile-header-height);
        left: 0;
        bottom: 0;
        height: calc(100vh - var(--mobile-header-height));
        max-height: calc(100vh - var(--mobile-header-height));
        z-index: 1000;
        box-shadow: 4px 0 24px rgba(0, 0, 0, 0.1);
        padding-top: 0.75rem;
        padding-bottom: 1rem;
        transform: translateX(-100%);
        width: var(--sidebar-width) !important;
        padding-left: var(--page-padding) !important;
        padding-right: var(--page-padding) !important;
    }

    .sidebar .brand-logo {
        display: none;
    }

    .sidebar .nav-btn {
        padding: 0.5rem 0.625rem;
        font-size: 0.85rem;
    }

    .sidebar .sub-nav-btn {
        font-size: 0.8rem;
        padding: 0.375rem 0.5rem;
    }

    .sidebar.sidebar-closed {
        transform: translateX(-100%);
    }

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

    .mobile-header {
        display: flex;
        position: fixed;
        top: 0;
        left: 0;
        right: 0;
        width: 100%;
        z-index: 1100;
        background-color: var(--color-surface);
    }

    .main-content {
        padding-top: var(--mobile-header-height);
    }
}

@media (max-width: 480px) {
    .sidebar .nav-btn {
        padding: 0.4375rem 0.5rem;
        font-size: 0.8125rem;
    }

    .sidebar .sub-nav-btn {
        font-size: 0.75rem;
    }
}

@media (max-width: 320px) {
    .mobile-header .brand-logo {
        font-size: 0.9375rem;
    }

    .menu-toggle .icon {
        width: 1.25rem;
        height: 1.25rem;
    }
}