:root {
    --primary-color: #FF2C55;
    --secondary-color: #00F2EA;
    --dark-color: #121212;
    --darker-color: #0A0A0A;
    --light-color: #ffffff;
    --gray-color: #888888;
    --light-gray-color: #CCCCCC;
    --overlay-color: rgba(0, 0, 0, 0.4);
    --gradient-overlay: linear-gradient(to top, rgba(0, 0, 0, 0.7) 0%, transparent 40%);
    --card-background: rgba(255, 255, 255, 0.08);
    --blur-effect: blur(10px);
    --transition-normal: all 0.3s cubic-bezier(0.19, 1, 0.22, 1);
    --transition-slow: all 0.5s cubic-bezier(0.19, 1, 0.22, 1);
    --shadow-normal: 0 4px 12px rgba(0, 0, 0, 0.15);
    --shadow-elevated: 0 8px 24px rgba(0, 0, 0, 0.2);
    --border-radius: 12px;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Nunito', 'PingFang SC', 'Helvetica Neue', Arial, sans-serif;
    background-color: var(--dark-color);
    color: var(--light-color);
    overflow: hidden;
    touch-action: pan-y;
    position: fixed;
    width: 100%;
    height: 100%;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

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

/* Main screens */
.screen {
    width: 100%;
    height: calc(100vh - 60px);
    position: absolute;
    left: 0;
    top: 0;
    transition: var(--transition-normal);
    opacity: 0;
    visibility: hidden;
    overflow-y: auto;
    overflow-x: hidden;
    -webkit-overflow-scrolling: touch;
    background-color: var(--darker-color);
}

.screen.active {
    opacity: 1;
    visibility: visible;
}

/* Video Feed Screen */
.video-feed {
    width: 100%;
    height: 100%;
    position: relative;
    overflow: hidden;
    background-color: black;
}

.video-card {
    width: 100%;
    height: 100%;
    position: absolute;
    left: 0;
    top: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    transition: var(--transition-slow);
}

video {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.video-overlay {
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 40%;
    background: var(--gradient-overlay);
    z-index: 5;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
    padding: 20px;
}

.action-buttons {
    position: absolute;
    right: 16px;
    bottom: 120px;
    display: flex;
    flex-direction: column;
    align-items: center;
    z-index: 10;
 }
 
 .action-button {
    width: 48px;
    height: 48px;
    background-color: rgba(255, 255, 255, 0.15);
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    margin-bottom: 20px;
    cursor: pointer;
    backdrop-filter: var(--blur-effect);
    -webkit-backdrop-filter: var(--blur-effect);
    border: 1px solid rgba(255, 255, 255, 0.2);
    box-shadow: var(--shadow-normal);
    transition: var(--transition-normal);
    position: relative;
 }
 
 .action-button:hover, .action-button:active {
    transform: scale(1.1);
    background-color: rgba(255, 255, 255, 0.25);
 }
 
 .action-button.like {
    background-color: rgba(255, 44, 85, 0.2);
 }
 
 .action-button.like.active {
    background-color: rgba(255, 44, 85, 0.6);
 }
 
 .action-button.favorite {
    background-color: rgba(255, 215, 0, 0.2);
 }
 
 .action-button.favorite.active {
    background-color: rgba(255, 215, 0, 0.6);
 }
 
 .action-count {
    position: absolute;
    bottom: -6px;
    font-size: 12px;
    font-weight: 600;
 }
 
 .action-label {
    font-size: 12px;
    margin-top: 5px;
    color: var(--light-color);
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.5);
 }
 
 .loading-screen {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: var(--dark-color);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    z-index: 1000;
 }
 
 .loading-spinner {
    width: 50px;
    height: 50px;
    border: 3px solid transparent;
    border-top: 3px solid var(--primary-color);
    border-right: 3px solid var(--secondary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin-bottom: 20px;
 }
 
 @keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
 }
 
 .loading-text {
    font-size: 16px;
    font-weight: 600;
    color: var(--light-color);
    text-align: center;
 }
 
 .swipe-indicator {
    position: absolute;
    bottom: 80px;
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    flex-direction: column;
    align-items: center;
    opacity: 0.8;
    z-index: 10;
    animation: pulse 2s infinite;
 }
 
 @keyframes pulse {
    0% { opacity: 0.4; transform: translateX(-50%) scale(0.95); }
    50% { opacity: 0.8; transform: translateX(-50%) scale(1); }
    100% { opacity: 0.4; transform: translateX(-50%) scale(0.95); }
 }
 
 .swipe-icon {
    width: 36px;
    height: 36px;
    margin-bottom: 8px;
 }
 
 .swipe-text {
    font-size: 14px;
    color: var(--light-color);
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.8);
    font-weight: 600;
 }
 
 .header {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 60px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 16px;
    z-index: 100;
    background: linear-gradient(to bottom, rgba(0,0,0,0.4) 0%, transparent 100%);
 }
 
 .app-title {
    display: flex;
    align-items: center;
    font-size: 22px;
    font-weight: 700;
    color: var(--light-color);
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.5);
 }
 
 .app-title .accent {
    color: var(--primary-color);
 }
 
 .logo-small {
    width: 28px;
    height: 28px;
    margin-right: 8px;
 }
 
 .progress-bar {
    position: absolute;
    top: 60px;
    left: 0;
    width: 100%;
    height: 3px;
    background-color: rgba(255, 255, 255, 0.2);
    z-index: 100;
 }
 
 .progress-fill {
    height: 100%;
    width: 0;
    background-color: var(--primary-color);
    transition: width 0.1s linear;
 }
 
 .video-info {
    padding: 12px 16px;
    position: relative;
    z-index: 10;
 }
 
 .video-title {
    font-size: 18px;
    font-weight: 700;
    margin-bottom: 8px;
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.7);
 }
 
 .video-desc {
    font-size: 14px;
    opacity: 0.9;
    margin-bottom: 12px;
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.7);
 }
 
 .video-meta {
    display: flex;
    align-items: center;
    font-size: 12px;
    opacity: 0.7;
 }
 
 .video-meta-item {
    margin-right: 16px;
    display: flex;
    align-items: center;
 }
 
 .video-meta-item svg {
    margin-right: 4px;
    width: 14px;
    height: 14px;
 }
 
 .play-pause-overlay {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%) scale(0);
    width: 80px;
    height: 80px;
    background-color: rgba(0, 0, 0, 0.5);
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 15;
    opacity: 0;
    transition: var(--transition-normal);
    backdrop-filter: var(--blur-effect);
    -webkit-backdrop-filter: var(--blur-effect);
 }
 
 .play-pause-overlay.visible {
    transform: translate(-50%, -50%) scale(1);
    opacity: 1;
 }
 
 .volume-control {
    position: absolute;
    right: 16px;
    top: 80px;
    width: 40px;
    height: 40px;
    background-color: rgba(255, 255, 255, 0.15);
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 10;
    cursor: pointer;
    backdrop-filter: var(--blur-effect);
    -webkit-backdrop-filter: var(--blur-effect);
    border: 1px solid rgba(255, 255, 255, 0.2);
    box-shadow: var(--shadow-normal);
 }
 
 /* Navigation Bar */
 .nav-bar {
    position: fixed;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 60px;
    background-color: rgba(18, 18, 18, 0.95);
    backdrop-filter: var(--blur-effect);
    -webkit-backdrop-filter: var(--blur-effect);
    display: flex;
    justify-content: space-around;
    align-items: center;
    z-index: 1000;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
 }
 
 .nav-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 8px 0;
    width: 25%;
    cursor: pointer;
 }
 
 .nav-icon {
    width: 24px;
    height: 24px;
    margin-bottom: 4px;
    transition: var(--transition-normal);
    color: var(--gray-color);
 }
 
 .nav-label {
    font-size: 12px;
    transition: var(--transition-normal);
    color: var(--gray-color);
 }
 
 .nav-item.active .nav-label {
    color: var(--primary-color);
 }
 
 .nav-item.active .nav-icon {
    color: var(--primary-color);
 }
 
 /* History Screen */
 .history-screen, .favorites-screen {
    background-color: var(--darker-color);
    padding: 70px 0 20px 0;
 }
 
 .screen-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 16px;
    margin-bottom: 20px;
 }
 
 .section-title {
    font-size: 24px;
    font-weight: 700;
 }
 
 .clear-btn {
    background-color: rgba(255, 255, 255, 0.1);
    border: none;
    padding: 8px 16px;
    border-radius: 20px;
    color: var(--light-gray-color);
    font-size: 14px;
    cursor: pointer;
    transition: var(--transition-normal);
 }
 
 .clear-btn:hover {
    background-color: rgba(255, 255, 255, 0.2);
 }
 
 .video-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 16px;
    padding: 0 16px 80px 16px;
 }
 
 .video-item {
    background-color: var(--card-background);
    border-radius: var(--border-radius);
    overflow: hidden;
    box-shadow: var(--shadow-normal);
    transition: var(--transition-normal);
    border: 1px solid rgba(255, 255, 255, 0.1);
 }
 
 .video-item:hover, .video-item:active {
    transform: translateY(-5px);
    box-shadow: var(--shadow-elevated);
 }
 
 .video-thumbnail {
    position: relative;
    width: 100%;
    padding-top: 177.77%; /* 16:9 aspect ratio */
    overflow: hidden;
    background-color: #333;
 }
 
 .video-thumbnail img {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    object-fit: cover;
 }
 
 .video-duration {
    position: absolute;
    bottom: 8px;
    right: 8px;
    background-color: rgba(0, 0, 0, 0.7);
    color: white;
    padding: 2px 6px;
    border-radius: 4px;
    font-size: 12px;
 }
 
 .video-item-info {
    padding: 10px;
 }
 
 .video-item-title {
    font-size: 14px;
    font-weight: 600;
    margin-bottom: 6px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
 }
 
 .video-item-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 12px;
    color: var(--gray-color);
 }
 
 .time-ago {
    display: flex;
    align-items: center;
 }
 
 .time-ago svg {
    width: 12px;
    height: 12px;
    margin-right: 4px;
 }
 
 /* Empty state */
 .empty-state {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 50vh;
    text-align: center;
    padding: 20px;
    color: var(--gray-color);
 }
 
 .empty-icon {
    width: 80px;
    height: 80px;
    margin-bottom: 20px;
    opacity: 0.5;
 }
 
 .empty-title {
    font-size: 20px;
    font-weight: 600;
    margin-bottom: 10px;
 }
 
 .empty-desc {
    font-size: 14px;
    max-width: 280px;
 }
 
 /* Profile Screen */
 .profile-screen {
    background-color: var(--darker-color);
    padding-top: 0;
 }
 
 .profile-header {
    height: 200px;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    position: relative;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
    align-items: center;
    padding-bottom: 24px;
 }
 
 .profile-avatar {
    width: 100px;
    height: 100px;
    border-radius: 50%;
    border: 4px solid white;
    overflow: hidden;
    margin-bottom: 12px;
    box-shadow: var(--shadow-elevated);
 }
 
 .profile-avatar img {
    width: 100%;
    height: 100%;
    object-fit: cover;
 }
 
 .profile-name {
    font-size: 22px;
    font-weight: 700;
    margin-bottom: 4px;
 }
 
 .profile-stats {
    display: flex;
    justify-content: space-around;
    align-items: center;
    width: 100%;
    padding: 20px 16px;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
 }
 
 .stat-item {
    display: flex;
    flex-direction: column;
    align-items: center;
 }
 
 .stat-value {
    font-size: 18px;
    font-weight: 700;
    margin-bottom: 4px;
 }
 
 .stat-label {
    font-size: 12px;
    color: var(--gray-color);
 }
 
 .profile-actions {
    display: flex;
    flex-direction: column;
    padding: 20px 16px 80px 16px;
 }
 
 .action-row {
    display: flex;
    align-items: center;
    padding: 16px 0;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    cursor: pointer;
 }
 
 .action-icon {
    width: 24px;
    height: 24px;
    margin-right: 16px;
    opacity: 0.8;
 }
 
 .action-text {
    flex: 1;
    font-size: 16px;
 }
 
 .action-arrow {
    width: 20px;
    height: 20px;
    opacity: 0.5;
 }
 
 /* Toast notification */
 .toast {
    position: fixed;
    top: 80px;
    left: 50%;
    transform: translateX(-50%);
    background-color: rgba(0, 0, 0, 0.8);
    color: white;
    padding: 10px 20px;
    border-radius: 30px;
    font-size: 14px;
    z-index: 2000;
    backdrop-filter: var(--blur-effect);
    -webkit-backdrop-filter: var(--blur-effect);
    opacity: 0;
    transition: var(--transition-normal);
    pointer-events: none;
 }
 
 .toast.show {
    opacity: 1;
 }
 
 /* Error page */
 .error-container {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: var(--darker-color);
 }
 
 .error-card {
    background-color: var(--dark-color);
    border-radius: var(--border-radius);
    padding: 40px;
    max-width: 90%;
    width: 400px;
    text-align: center;
    box-shadow: var(--shadow-elevated);
 }
 
 .logo {
    width: 80px;
    height: 80px;
    margin-bottom: 20px;
 }
 
 .button {
    display: inline-block;
    margin-top: 20px;
    padding: 10px 20px;
    background-color: var(--primary-color);
    color: white;
    text-decoration: none;
    border-radius: 30px;
    font-weight: 600;
    transition: var(--transition-normal);
 }
 
 .button:hover {
    background-color: #ff4d6e;
    transform: translateY(-2px);
 }
 
 /* Animation for card transition */
 @keyframes slideInUp {
    from {
        transform: translateY(100%);
    }
    to {
        transform: translateY(0);
    }
 }
 
 .slide-in {
    animation: slideInUp 0.5s cubic-bezier(0.19, 1, 0.22, 1);
 }
 
 /* Responsive adjustments */
 @media (min-width: 768px) {
    .video-grid {
        grid-template-columns: repeat(3, 1fr);
    }
 }
 
 @media (min-width: 1024px) {
    .video-grid {
        grid-template-columns: repeat(4, 1fr);
    }
 }