/* CSS Variables & Design Tokens */
:root {
    /* Colors - Light Instagram Theme */
    --bg-primary: #ffffff;
    --bg-secondary: #fafafa;
    --bg-tertiary: #f0f0f0;
    --text-primary: #262626;
    --text-secondary: #8e8e8e;
    --text-tertiary: #c7c7c7;
    --border-color: #dbdbdb;
    --border-light: #efefef;
    --accent-primary: #0095f6;
    --accent-hover: #1877f2;
    --accent-light: #e0f1ff;
    --like-color: #ed4956;
    --story-ring: linear-gradient(45deg, #f09433 0%, #e6683c 25%, #dc2743 50%, #cc2366 75%, #bc1888 100%);
    
    /* Typography */
    --font-display: 'Playfair Display', serif;
    --font-body: 'Plus Jakarta Sans', -apple-system, BlinkMacSystemFont, sans-serif;
    
    /* Spacing */
    --spacing-xs: 4px;
    --spacing-sm: 8px;
    --spacing-md: 16px;
    --spacing-lg: 24px;
    --spacing-xl: 32px;
    
    /* Border Radius */
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-full: 50%;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.12);
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 250ms ease;
    --transition-slow: 350ms ease;
}

/* Reset & Base */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-body);
    background-color: var(--bg-secondary);
    color: var(--text-primary);
    line-height: 1.5;
    min-height: 100vh;
}

/* Top Navigation */
.top-nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background-color: var(--bg-primary);
    border-bottom: 1px solid var(--border-light);
    z-index: 100;
    height: 60px;
}

.nav-container {
    max-width: 975px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo-text {
    font-family: var(--font-display);
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--text-primary);
    letter-spacing: -0.5px;
}

.search-bar {
    display: none;
    align-items: center;
    background-color: var(--bg-secondary);
    border-radius: var(--radius-md);
    padding: var(--spacing-xs) var(--spacing-md);
    width: 268px;
}

.search-bar .search-icon {
    width: 16px;
    height: 16px;
    color: var(--text-secondary);
    margin-right: var(--spacing-sm);
}

.search-bar input {
    border: none;
    background: transparent;
    outline: none;
    font-size: 0.875rem;
    color: var(--text-primary);
    width: 100%;
}

.search-bar input::placeholder {
    color: var(--text-secondary);
}

.nav-icons {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

.nav-btn {
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--spacing-xs);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: transform var(--transition-fast);
}

.nav-btn:hover {
    transform: scale(1.05);
}

.nav-btn svg {
    width: 24px;
    height: 24px;
    color: var(--text-primary);
}

.nav-btn.active svg {
    fill: var(--text-primary);
    stroke: none;
}

.nav-btn.profile-btn {
    padding: 0;
}

.nav-btn.profile-btn img {
    width: 28px;
    height: 28px;
    border-radius: var(--radius-full);
    object-fit: cover;
}

/* Notification Badge */
.notification-badge {
    position: absolute;
    top: -2px;
    right: -2px;
    background-color: var(--like-color);
    color: white;
    font-size: 0.625rem;
    font-weight: 600;
    min-width: 18px;
    height: 18px;
    border-radius: 9px;
    display: flex;
    align-items: center;
    justify-content: center;
    border: 2px solid var(--bg-primary);
}

.messages-btn,
.notifications-btn {
    position: relative;
}

/* Inbox Dropdown */
.inbox-dropdown,
.notifications-dropdown {
    position: absolute;
    top: 60px;
    right: 20px;
    width: 380px;
    max-height: 500px;
    background-color: var(--bg-primary);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    z-index: 101;
    display: none;
    overflow: hidden;
}

.inbox-dropdown.active,
.notifications-dropdown.active {
    display: block;
    animation: slideDown 0.2s ease;
}

@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.dropdown-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-md);
    border-bottom: 1px solid var(--border-light);
}

.dropdown-header h3 {
    font-size: 1rem;
    font-weight: 600;
}

.new-message-btn,
.mark-read-btn {
    background: none;
    border: none;
    color: var(--accent-primary);
    font-weight: 600;
    font-size: 0.875rem;
    cursor: pointer;
}

.new-message-btn {
    padding: var(--spacing-xs);
}

.new-message-btn svg {
    width: 20px;
    height: 20px;
    stroke: var(--text-primary);
}

/* Messages List */
.messages-list,
.notifications-list {
    max-height: 400px;
    overflow-y: auto;
}

.message-item,
.notification-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    cursor: pointer;
    transition: background-color var(--transition-fast);
}

.message-item:hover,
.notification-item:hover {
    background-color: var(--bg-secondary);
}

.message-item.unread,
.notification-item.unread {
    background-color: var(--accent-light);
}

.message-item.unread:hover,
.notification-item.unread:hover {
    background-color: #d4ebff;
}

.message-content {
    flex: 1;
    min-width: 0;
}

.message-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2px;
}

.message-header .username {
    font-weight: 600;
    font-size: 0.875rem;
}

.message-time,
.notification-time {
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.message-preview {
    font-size: 0.875rem;
    color: var(--text-secondary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

/* Notifications */
.notification-content {
    flex: 1;
    min-width: 0;
}

.notification-content p {
    font-size: 0.875rem;
    line-height: 1.4;
}

.notification-content .username {
    font-weight: 600;
}

.notification-preview {
    width: 44px;
    height: 44px;
    border-radius: var(--radius-sm);
    overflow: hidden;
    flex-shrink: 0;
}

.notification-preview img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.follow-back-btn {
    background-color: var(--accent-primary);
    color: white;
    border: none;
    border-radius: var(--radius-sm);
    padding: var(--spacing-xs) var(--spacing-md);
    font-weight: 600;
    font-size: 0.75rem;
    cursor: pointer;
}

.follow-back-btn:hover {
    background-color: var(--accent-hover);
}

/* Main Content */
.main-content {
    padding-top: 84px;
    padding-bottom: 60px;
}

.content-wrapper {
    max-width: 975px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--spacing-xl);
}

/* Stories */
.stories-container {
    background-color: var(--bg-primary);
    border: 1px solid var(--border-light);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
    margin-bottom: var(--spacing-md);
    overflow: hidden;
}

.stories-track {
    display: flex;
    gap: var(--spacing-md);
    overflow-x: auto;
    scrollbar-width: none;
    -ms-overflow-style: none;
    padding-bottom: var(--spacing-xs);
}

.stories-track::-webkit-scrollbar {
    display: none;
}

.story-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-xs);
    cursor: pointer;
    flex-shrink: 0;
    transition: transform var(--transition-fast);
}

.story-item:hover {
    transform: scale(1.02);
}

.story-avatar {
    position: relative;
    width: 66px;
    height: 66px;
}

.story-avatar img {
    width: 100%;
    height: 100%;
    border-radius: var(--radius-full);
    object-fit: cover;
    border: 2px solid var(--bg-primary);
}

.add-story .story-avatar {
    background-color: var(--bg-secondary);
    border-radius: var(--radius-full);
    display: flex;
    align-items: center;
    justify-content: center;
}

.add-icon {
    position: absolute;
    bottom: 0;
    right: 0;
    width: 20px;
    height: 20px;
    background-color: var(--accent-primary);
    color: white;
    border-radius: var(--radius-full);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 14px;
    font-weight: 600;
    border: 2px solid var(--bg-primary);
}

.story-ring {
    width: 66px;
    height: 66px;
    border-radius: var(--radius-full);
    padding: 3px;
    background: var(--story-ring);
}

.story-ring img {
    width: 100%;
    height: 100%;
    border-radius: var(--radius-full);
    object-fit: cover;
    border: 2px solid var(--bg-primary);
}

.story-username {
    font-size: 0.75rem;
    color: var(--text-primary);
    max-width: 66px;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

/* Posts Feed */
.posts-feed {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.post {
    background-color: var(--bg-primary);
    border: 1px solid var(--border-light);
    border-radius: var(--radius-md);
    overflow: hidden;
}

.post-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-sm) var(--spacing-md);
}

.post-user {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.user-avatar {
    width: 36px;
    height: 36px;
    border-radius: var(--radius-full);
    overflow: hidden;
}

.user-avatar.large {
    width: 56px;
    height: 56px;
}

.user-avatar.small {
    width: 28px;
    height: 28px;
}

.user-avatar img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.user-info {
    display: flex;
    flex-direction: column;
}

.user-info .username {
    font-weight: 600;
    font-size: 0.875rem;
    color: var(--text-primary);
}

.user-info .location {
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.more-btn {
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--spacing-xs);
}

.more-btn svg {
    width: 20px;
    height: 20px;
    color: var(--text-primary);
}

.post-image {
    width: 100%;
    aspect-ratio: 4/5;
    overflow: hidden;
    background-color: var(--bg-tertiary);
}

.post-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.post-actions {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-sm) var(--spacing-md);
    padding-bottom: var(--spacing-xs);
}

.action-left {
    display: flex;
    gap: var(--spacing-md);
}

.action-btn {
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--spacing-xs);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: transform var(--transition-fast), color var(--transition-fast);
}

.action-btn:hover {
    transform: scale(1.1);
}

.action-btn svg {
    width: 24px;
    height: 24px;
    color: var(--text-primary);
}

.action-btn.like-btn.liked svg {
    fill: var(--like-color);
    stroke: var(--like-color);
    animation: heartBeat 0.3s ease;
}

@keyframes heartBeat {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.2); }
}

.post-stats {
    padding: 0 var(--spacing-md);
    margin-bottom: var(--spacing-xs);
}

.likes-count {
    font-weight: 600;
    font-size: 0.875rem;
}

.post-caption {
    padding: 0 var(--spacing-md);
    margin-bottom: var(--spacing-xs);
}

.post-caption .username {
    font-weight: 600;
    margin-right: var(--spacing-xs);
}

.post-caption .caption-text {
    font-size: 0.875rem;
}

.post-comments {
    padding: 0 var(--spacing-md);
    margin-bottom: var(--spacing-xs);
}

.view-comments {
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 0.875rem;
    cursor: pointer;
    padding: 0;
    margin-bottom: var(--spacing-xs);
}

.view-comments:hover {
    color: var(--text-primary);
}

.comment {
    font-size: 0.875rem;
    margin-bottom: var(--spacing-xs);
}

.comment .username {
    font-weight: 600;
    margin-right: var(--spacing-xs);
}

.post-time {
    padding: 0 var(--spacing-md);
    font-size: 0.625rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    margin-bottom: var(--spacing-sm);
}

.add-comment {
    display: flex;
    align-items: center;
    padding: var(--spacing-sm) var(--spacing-md);
    border-top: 1px solid var(--border-light);
}

.add-comment input {
    flex: 1;
    border: none;
    background: transparent;
    outline: none;
    font-size: 0.875rem;
    padding: var(--spacing-xs) 0;
}

.add-comment input::placeholder {
    color: var(--text-secondary);
}

.post-btn {
    background: none;
    border: none;
    color: var(--accent-primary);
    font-weight: 600;
    font-size: 0.875rem;
    cursor: pointer;
    opacity: 0.5;
    transition: opacity var(--transition-fast);
}

.post-btn:not(:disabled) {
    opacity: 1;
}

/* Sidebar */
.sidebar {
    display: none;
}

.sidebar-content {
    position: sticky;
    top: 100px;
}

.current-user {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
}

.current-user .user-details {
    flex: 1;
}

.current-user .username {
    font-weight: 600;
    display: block;
}

.current-user .full-name {
    color: var(--text-secondary);
    font-size: 0.875rem;
}

.switch-btn {
    background: none;
    border: none;
    color: var(--accent-primary);
    font-weight: 600;
    font-size: 0.75rem;
    cursor: pointer;
}

.suggestions {
    margin-bottom: var(--spacing-lg);
}

.suggestions-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-md);
}

.suggestions-header span {
    color: var(--text-secondary);
    font-weight: 600;
    font-size: 0.875rem;
}

.see-all {
    background: none;
    border: none;
    color: var(--text-primary);
    font-weight: 600;
    font-size: 0.75rem;
    cursor: pointer;
}

.suggestion-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.suggestion-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.suggestion-item .user-details {
    flex: 1;
}

.suggestion-item .username {
    font-weight: 600;
    font-size: 0.875rem;
    display: block;
}

.suggestion-item .relation {
    color: var(--text-secondary);
    font-size: 0.75rem;
}

.follow-btn {
    background: none;
    border: none;
    color: var(--accent-primary);
    font-weight: 600;
    font-size: 0.75rem;
    cursor: pointer;
}

.follow-btn:hover {
    color: var(--accent-hover);
}

.follow-btn.following {
    color: var(--text-secondary);
}

.sidebar-footer {
    margin-top: var(--spacing-xl);
}

.footer-links {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-xs) var(--spacing-sm);
    margin-bottom: var(--spacing-md);
}

.footer-links a {
    color: var(--text-tertiary);
    text-decoration: none;
    font-size: 0.75rem;
}

.footer-links a:hover {
    text-decoration: underline;
}

.footer-links a::after {
    content: "·";
    margin-left: var(--spacing-sm);
    color: var(--text-tertiary);
}

.footer-links a:last-child::after {
    content: none;
}

.copyright {
    color: var(--text-tertiary);
    font-size: 0.75rem;
    text-transform: uppercase;
}

/* Mobile Navigation */
.mobile-nav {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background-color: var(--bg-primary);
    border-top: 1px solid var(--border-light);
    display: flex;
    justify-content: space-around;
    align-items: center;
    height: 50px;
    z-index: 100;
    padding: 0 var(--spacing-md);
}

.mobile-nav-btn {
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--spacing-xs);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-primary);
    transition: transform var(--transition-fast);
}

.mobile-nav-btn:hover {
    transform: scale(1.1);
}

.mobile-nav-btn svg {
    width: 24px;
    height: 24px;
}

.mobile-nav-btn.active svg {
    fill: var(--text-primary);
    stroke: none;
}

.mobile-nav-btn.create-btn svg {
    width: 28px;
    height: 28px;
}

.mobile-nav-btn.profile-btn img {
    width: 28px;
    height: 28px;
    border-radius: var(--radius-full);
    object-fit: cover;
}

/* Story Modal */
.story-modal {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: #1a1a1a;
    z-index: 1000;
    display: none;
    align-items: center;
    justify-content: center;
}

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

.story-viewer {
    width: 100%;
    max-width: 450px;
    height: 100%;
    max-height: 800px;
    position: relative;
    display: flex;
    flex-direction: column;
}

.story-progress {
    position: absolute;
    top: var(--spacing-md);
    left: var(--spacing-md);
    right: var(--spacing-md);
    display: flex;
    gap: var(--spacing-xs);
    z-index: 10;
}

.progress-bar {
    flex: 1;
    height: 2px;
    background-color: rgba(255, 255, 255, 0.3);
    border-radius: 2px;
    overflow: hidden;
}

.progress-bar::after {
    content: '';
    display: block;
    height: 100%;
    width: 0;
    background-color: white;
    transition: width 0.1s linear;
}

.progress-bar.active::after {
    width: 100%;
    animation: progress 5s linear;
}

@keyframes progress {
    from { width: 0; }
    to { width: 100%; }
}

.story-header {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    padding: var(--spacing-lg) var(--spacing-md) var(--spacing-md);
    display: flex;
    align-items: center;
    justify-content: space-between;
    background: linear-gradient(to bottom, rgba(0,0,0,0.4), transparent);
    z-index: 10;
}

.story-user {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    color: white;
}

.story-user .username {
    font-weight: 600;
    font-size: 0.875rem;
}

.story-time {
    color: rgba(255, 255, 255, 0.7);
    font-size: 0.75rem;
}

.close-story {
    background: none;
    border: none;
    color: white;
    cursor: pointer;
    padding: var(--spacing-xs);
}

.close-story svg {
    width: 24px;
    height: 24px;
}

.story-image {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: hidden;
}

.story-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.story-footer {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    padding: var(--spacing-md);
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    background: linear-gradient(to top, rgba(0,0,0,0.4), transparent);
}

.story-input {
    flex: 1;
}

.story-input input {
    width: 100%;
    background: rgba(255, 255, 255, 0.2);
    border: 1px solid rgba(255, 255, 255, 0.3);
    border-radius: 20px;
    padding: var(--spacing-sm) var(--spacing-md);
    color: white;
    outline: none;
    font-size: 0.875rem;
}

.story-input input::placeholder {
    color: rgba(255, 255, 255, 0.7);
}

.story-action {
    background: none;
    border: none;
    color: white;
    cursor: pointer;
    padding: var(--spacing-xs);
}

.story-action svg {
    width: 28px;
    height: 28px;
    fill: none;
}

/* Responsive Design */
@media (min-width: 640px) {
    .search-bar {
        display: flex;
    }
    
    .nav-icons {
        gap: var(--spacing-lg);
    }
}

@media (min-width: 1024px) {
    .content-wrapper {
        grid-template-columns: 1fr 320px;
    }
    
    .sidebar {
        display: block;
    }
    
    .mobile-nav {
        display: none;
    }
    
    .main-content {
        padding-bottom: var(--spacing-xl);
    }
}

/* Utility Classes */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* Loading Animation */
@keyframes shimmer {
    0% { background-position: -200% 0; }
    100% { background-position: 200% 0; }
}

.loading {
    background: linear-gradient(90deg, var(--bg-secondary) 25%, var(--bg-tertiary) 50%, var(--bg-secondary) 75%);
    background-size: 200% 100%;
    animation: shimmer 1.5s infinite;
}