/* ==========================================================================
   Django Student Management System - Main Stylesheet
   Static file: static/css/style.css
   Pure CSS3 with modern CSS custom properties (Design Tokens)
   ========================================================================== */

:root {
    /* Color Palette (60-30-10 Rule) */
    --color-bg: #f8fafc;
    --color-surface: #ffffff;
    --color-surface-hover: #f1f5f9;
    --color-surface-subtle: #f8fafc;
    
    /* Text & Neutral Hierarchy */
    --color-text-main: #0f172a;
    --color-text-muted: #64748b;
    --color-text-subtle: #94a3b8;
    --color-border: #e2e8f0;
    --color-border-dark: #cbd5e1;
    
    /* Brand & Accent (10% Budget) */
    --color-primary: #1e3a8a;          /* Deep academic blue */
    --color-primary-light: #2563eb;
    --color-primary-subtle: #eff6ff;
    --color-primary-hover: #1e40af;
    
    /* Semantic Status Colors */
    --color-success: #15803d;
    --color-success-bg: #f0fdf4;
    --color-success-border: #bbf7d0;
    
    --color-warning: #b45309;
    --color-warning-bg: #fffbeb;
    --color-warning-border: #fde68a;
    
    --color-danger: #b91c1c;
    --color-danger-bg: #fef2f2;
    --color-danger-border: #fecaca;
    
    --color-info: #0369a1;
    --color-info-bg: #f0f9ff;
    --color-info-border: #bae6fd;
    
    /* Layout Dimensions */
    --sidebar-width: 260px;
    --header-height: 64px;
    --footer-height: 52px;
    
    /* Radii */
    --radius-sm: 4px;
    --radius-md: 6px;
    --radius-lg: 8px;
    --radius-full: 9999px;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -4px rgba(0, 0, 0, 0.05);
    
    /* Typography */
    --font-sans: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
    
    /* Transitions */
    --transition-fast: 150ms cubic-bezier(0.16, 1, 0.3, 1);
    --transition-normal: 200ms cubic-bezier(0.16, 1, 0.3, 1);
}

/* Base Reset */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    font-size: 15px;
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-sans);
    color: var(--color-text-main);
    background-color: var(--color-bg);
    min-height: 100vh;
    overflow-x: hidden;
}


a {
    color: var(--color-primary-light);
    text-decoration: none;
    transition: color var(--transition-fast);
}

a:hover {
    color: var(--color-primary-hover);
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

/* Numbers & Tabular Discipline */
.tabular-nums, .stat-value, .table-col-num, .badge-count {
    font-variant-numeric: tabular-nums;
    font-feature-settings: "tnum";
}

/* ==========================================================================
   Layout Shell
   ========================================================================== */

.app-layout {
    display: flex;
    min-height: 100vh;
}

.main-wrapper {
    flex: 1;
    display: flex;
    flex-direction: column;
    min-width: 0;
    margin-left: var(--sidebar-width);
    transition: margin-left var(--transition-normal);
}

.main-content {
    flex: 1;
    padding: 1.5rem 2rem;
    max-width: 1500px;
    width: 100%;
    margin: 0 auto;
}

/* Mobile Sidebar Backdrop */
.sidebar-backdrop {
    display: none;
    position: fixed;
    inset: 0;
    background-color: rgba(15, 23, 42, 0.5);
    z-index: 40;
    opacity: 0;
    transition: opacity var(--transition-normal);
}

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

/* ==========================================================================
   Sidebar Component
   ========================================================================== */

.app-sidebar {
    position: fixed;
    top: 0;
    bottom: 0;
    left: 0;
    width: var(--sidebar-width);
    background-color: var(--color-surface);
    border-right: 1px solid var(--color-border);
    display: flex;
    flex-direction: column;
    z-index: 50;
    transition: transform var(--transition-normal);
}

.app-layout.sidebar-collapsed .app-sidebar {
    transform: translateX(-100%);
}

.app-layout.sidebar-collapsed .main-wrapper {
    margin-left: 0;
}

.sidebar-header {
    height: var(--header-height);
    display: flex;
    align-items: center;
    padding: 0 1.25rem;
    border-bottom: 1px solid var(--color-border);
    gap: 0.75rem;
}

.sidebar-brand-icon {
    width: 32px;
    height: 32px;
    background-color: var(--color-primary);
    color: #ffffff;
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 0.95rem;
    flex-shrink: 0;
}

.sidebar-brand-text {
    font-size: 1rem;
    font-weight: 700;
    color: var(--color-text-main);
    letter-spacing: -0.01em;
    white-space: nowrap;
}

.sidebar-role-indicator {
    padding: 0.75rem 1.25rem;
    border-bottom: 1px solid var(--color-border);
    background-color: var(--color-surface-subtle);
}

.role-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--color-primary);
}

.role-badge::before {
    content: "";
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background-color: var(--color-primary-light);
}

.sidebar-nav {
    flex: 1;
    overflow-y: auto;
    padding: 1rem 0.75rem;
}

.nav-section-title {
    font-size: 0.7rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--color-text-subtle);
    padding: 0.75rem 0.75rem 0.35rem;
    margin-top: 0.5rem;
}

.nav-section-title:first-child {
    margin-top: 0;
}

.nav-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 0.2rem;
}

.nav-item a {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.55rem 0.75rem;
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--color-text-muted);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
    white-space: nowrap;
}

.nav-item a:hover {
    color: var(--color-text-main);
    background-color: var(--color-surface-hover);
}

.nav-item.active a {
    color: var(--color-primary);
    background-color: var(--color-primary-subtle);
    font-weight: 600;
}

.nav-icon {
    width: 18px;
    text-align: center;
    color: var(--color-text-subtle);
    font-size: 0.95rem;
}

.nav-item.active .nav-icon {
    color: var(--color-primary);
}

.sidebar-footer {
    padding: 1rem 1.25rem;
    border-top: 1px solid var(--color-border);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.sidebar-user {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    min-width: 0;
}

.user-avatar-sm {
    width: 32px;
    height: 32px;
    border-radius: 50%;
    background-color: var(--color-border);
    color: var(--color-text-muted);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 0.8rem;
    flex-shrink: 0;
}

.user-details-sm {
    min-width: 0;
    overflow: hidden;
}

.user-name-sm {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--color-text-main);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.user-role-sm {
    font-size: 0.75rem;
    color: var(--color-text-muted);
}

/* ==========================================================================
   Navbar Component (Top Bar Contract)
   Zone 1: Left Affordance & Context
   Zone 2: Search & Center Context
   Zone 3: Actions & Profile Menu
   ========================================================================== */

.app-navbar {
    height: var(--header-height);
    background-color: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 2rem;
    position: sticky;
    top: 0;
    z-index: 30;
}

.navbar-zone-left {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.sidebar-toggle-btn {
    background: none;
    border: none;
    color: var(--color-text-muted);
    font-size: 1.1rem;
    cursor: pointer;
    padding: 0.4rem;
    border-radius: var(--radius-sm);
    display: inline-flex;
    align-items: center;
    justify-content: center;
}

.sidebar-toggle-btn:hover {
    color: var(--color-text-main);
    background-color: var(--color-surface-hover);
}

.navbar-session-pill {
    font-size: 0.8rem;
    color: var(--color-text-muted);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.navbar-session-pill strong {
    color: var(--color-text-main);
    font-weight: 600;
}

.navbar-zone-right {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.user-dropdown {
    position: relative;
}

.user-dropdown-btn {
    background: none;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-full);
    padding: 0.35rem 0.75rem 0.35rem 0.4rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
    transition: background-color var(--transition-fast);
}

.user-dropdown-btn:hover {
    background-color: var(--color-surface-hover);
}

.dropdown-menu {
    display: none;
    position: absolute;
    right: 0;
    top: calc(100% + 8px);
    width: 200px;
    background-color: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    padding: 0.5rem 0;
    z-index: 50;
    list-style: none;
}

.dropdown-menu.active {
    display: block;
}

.dropdown-item {
    display: flex;
    align-items: center;
    gap: 0.6rem;
    padding: 0.55rem 1rem;
    font-size: 0.85rem;
    color: var(--color-text-main);
    transition: background-color var(--transition-fast);
}

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

.dropdown-divider {
    height: 1px;
    background-color: var(--color-border);
    margin: 0.4rem 0;
}

/* ==========================================================================
   Breadcrumbs Component
   ========================================================================== */

.app-breadcrumbs {
    padding: 0.85rem 2rem 0;
    max-width: 1500px;
    width: 100%;
    margin: 0 auto;
}

.breadcrumb-list {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    list-style: none;
    font-size: 0.8rem;
    color: var(--color-text-muted);
}

.breadcrumb-item a {
    color: var(--color-text-muted);
}

.breadcrumb-item a:hover {
    color: var(--color-text-main);
}

.breadcrumb-separator {
    color: var(--color-text-subtle);
    user-select: none;
}

.breadcrumb-item.active {
    color: var(--color-text-main);
    font-weight: 600;
}

/* ==========================================================================
   Messages / Alerts Component (Django Messages)
   ========================================================================== */

.app-messages {
    padding: 0.75rem 2rem 0;
    max-width: 1500px;
    width: 100%;
    margin: 0 auto;
}

.alert {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0.75rem 1rem;
    border-radius: var(--radius-md);
    font-size: 0.875rem;
    margin-bottom: 0.75rem;
    border: 1px solid transparent;
}

.alert-content {
    display: flex;
    align-items: center;
    gap: 0.6rem;
}

.alert-dismiss {
    background: none;
    border: none;
    font-size: 1.1rem;
    cursor: pointer;
    color: inherit;
    opacity: 0.7;
    line-height: 1;
}

.alert-dismiss:hover {
    opacity: 1;
}

.alert-success {
    background-color: var(--color-success-bg);
    border-color: var(--color-success-border);
    color: var(--color-success);
}

.alert-warning {
    background-color: var(--color-warning-bg);
    border-color: var(--color-warning-border);
    color: var(--color-warning);
}

.alert-danger {
    background-color: var(--color-danger-bg);
    border-color: var(--color-danger-border);
    color: var(--color-danger);
}

.alert-info {
    background-color: var(--color-info-bg);
    border-color: var(--color-info-border);
    color: var(--color-info);
}

/* ==========================================================================
   Cards & Content Containers
   ========================================================================== */

.card {
    background-color: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    margin-bottom: 1.5rem;
}

.card-header {
    padding: 1rem 1.25rem;
    border-bottom: 1px solid var(--color-border);
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
}

.card-title {
    font-size: 1rem;
    font-weight: 600;
    color: var(--color-text-main);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.card-subtitle {
    font-size: 0.8rem;
    color: var(--color-text-muted);
    margin-top: 0.15rem;
}

.card-body {
    padding: 1.25rem;
}

.card-footer {
    padding: 0.85rem 1.25rem;
    border-top: 1px solid var(--color-border);
    background-color: var(--color-surface-subtle);
    border-bottom-left-radius: var(--radius-lg);
    border-bottom-right-radius: var(--radius-lg);
}

/* Page Header Block */
.page-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
}

.page-title {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--color-text-main);
    letter-spacing: -0.02em;
}

.page-description {
    font-size: 0.875rem;
    color: var(--color-text-muted);
    margin-top: 0.2rem;
}

.page-actions {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

/* ==========================================================================
   Buttons
   ========================================================================== */

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.55rem 1rem;
    font-size: 0.875rem;
    font-weight: 500;
    border-radius: var(--radius-md);
    border: 1px solid transparent;
    cursor: pointer;
    transition: all var(--transition-fast);
    white-space: nowrap;
    text-decoration: none;
    line-height: 1.2;
}

.btn-primary {
    background-color: var(--color-primary);
    color: #ffffff;
    border-color: var(--color-primary);
}

.btn-primary:hover {
    background-color: var(--color-primary-hover);
    color: #ffffff;
}

.btn-secondary {
    background-color: var(--color-surface);
    color: var(--color-text-main);
    border-color: var(--color-border);
}

.btn-secondary:hover {
    background-color: var(--color-surface-hover);
    border-color: var(--color-border-dark);
    color: var(--color-text-main);
}

.btn-outline {
    background-color: transparent;
    color: var(--color-primary);
    border-color: var(--color-primary);
}

.btn-outline:hover {
    background-color: var(--color-primary-subtle);
}

.btn-danger {
    background-color: var(--color-danger);
    color: #ffffff;
    border-color: var(--color-danger);
}

.btn-danger:hover {
    background-color: #991b1b;
    color: #ffffff;
}

.btn-sm {
    padding: 0.35rem 0.65rem;
    font-size: 0.8rem;
}

.btn-icon {
    padding: 0.45rem;
    font-size: 0.9rem;
    border-radius: var(--radius-sm);
}

/* ==========================================================================
   Badges & Tags (Zero-Pill Restraint)
   ========================================================================== */

.badge {
    display: inline-flex;
    align-items: center;
    gap: 0.3rem;
    font-size: 0.75rem;
    font-weight: 500;
    padding: 0.2rem 0.55rem;
    border-radius: var(--radius-sm);
    line-height: 1.2;
}

.badge-active, .badge-status-active {
    background-color: var(--color-success-bg);
    color: var(--color-success);
    border: 1px solid var(--color-success-border);
}

.badge-inactive, .badge-status-left {
    background-color: var(--color-danger-bg);
    color: var(--color-danger);
    border: 1px solid var(--color-danger-border);
}

.badge-status-graduated {
    background-color: var(--color-info-bg);
    color: var(--color-info);
    border: 1px solid var(--color-info-border);
}

.badge-session {
    background-color: var(--color-primary-subtle);
    color: var(--color-primary);
    border: 1px solid #bfdbfe;
    font-weight: 600;
}

.badge-gender {
    background-color: var(--color-surface-hover);
    color: var(--color-text-muted);
    border: 1px solid var(--color-border);
}

/* ==========================================================================
   Modal Dialog
   ========================================================================== */

.modal-backdrop {
    display: none;
    position: fixed;
    inset: 0;
    background-color: rgba(15, 23, 42, 0.6);
    backdrop-filter: blur(2px);
    z-index: 100;
    align-items: center;
    justify-content: center;
    padding: 1.5rem;
}

.modal-backdrop.active {
    display: flex;
}

.modal-dialog {
    background-color: var(--color-surface);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    width: 100%;
    max-width: 520px;
    border: 1px solid var(--color-border);
    animation: modalSlide 180ms cubic-bezier(0.16, 1, 0.3, 1);
}

@keyframes modalSlide {
    from {
        opacity: 0;
        transform: translateY(-12px) scale(0.98);
    }
    to {
        opacity: 1;
        transform: translateY(0) scale(1);
    }
}

.modal-header {
    padding: 1.1rem 1.25rem;
    border-bottom: 1px solid var(--color-border);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.modal-title {
    font-size: 1.05rem;
    font-weight: 600;
    color: var(--color-text-main);
}

.modal-close-btn {
    background: none;
    border: none;
    font-size: 1.25rem;
    color: var(--color-text-muted);
    cursor: pointer;
    line-height: 1;
}

.modal-close-btn:hover {
    color: var(--color-text-main);
}

.modal-body {
    padding: 1.25rem;
    font-size: 0.9rem;
    color: var(--color-text-muted);
}

.modal-footer {
    padding: 1rem 1.25rem;
    border-top: 1px solid var(--color-border);
    background-color: var(--color-surface-subtle);
    display: flex;
    align-items: center;
    justify-content: flex-end;
    gap: 0.75rem;
    border-bottom-left-radius: var(--radius-lg);
    border-bottom-right-radius: var(--radius-lg);
}

/* ==========================================================================
   Footer Component
   ========================================================================== */

.app-footer {
    height: var(--footer-height);
    background-color: var(--color-surface);
    border-top: 1px solid var(--color-border);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 2rem;
    font-size: 0.8rem;
    color: var(--color-text-muted);
}

.footer-copy {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.footer-links {
    display: flex;
    gap: 1rem;
    list-style: none;
}

.footer-links a {
    color: var(--color-text-muted);
}

.footer-links a:hover {
    color: var(--color-text-main);
}

/* ==========================================================================
   Responsive Adaptations
   ========================================================================== */

@media (max-width: 1024px) {
    :root {
        --sidebar-width: 0px;
    }

    .app-sidebar {
        transform: translateX(-100%);
        width: 260px;
    }

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

    .app-layout.sidebar-collapsed .app-sidebar {
        transform: translateX(-100%);
    }

    .app-layout:not(.sidebar-collapsed) .app-sidebar.active {
        transform: translateX(0);
    }

    .main-wrapper {
        margin-left: 0;
    }

    .main-content {
        padding: 1.25rem 1rem;
    }

    .app-navbar {
        padding: 0 1rem;
    }
}