:root {
    --primary-color: #6366f1;
    --primary-dark: #4f46e5;
    --secondary-color: #8b5cf6;
    --success-color: #10b981;
    --danger-color: #ef4444;
    --warning-color: #f59e0b;
    
    --bg-primary: #ffffff;
    --bg-secondary: #f9fafb;
    --bg-tertiary: #f3f4f6;
    --text-primary: #111827;
    --text-secondary: #6b7280;
    --text-tertiary: #9ca3af;
    --border-color: #e5e7eb;
    
    --sidebar-width: 280px;
    --header-height: 64px;
    --footer-height: 80px;
    --border-radius: 12px;
    
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
    
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.dark-mode {
    --bg-primary: #1f2937;
    --bg-secondary: #111827;
    --bg-tertiary: #374151;
    --text-primary: #f9fafb;
    --text-secondary: #d1d5db;
    --text-tertiary: #9ca3af;
    --border-color: #374151;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

body {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 16px;
}

.app-container {
    width: 100%;
    max-width: 1400px;
    height: 90vh;
    background: var(--bg-primary);
    border-radius: 24px;
    box-shadow: var(--shadow-lg);
    display: flex;
    overflow: hidden;
    position: relative;
    transition: var(--transition);
}

/* Sidebar Styles */
.sidebar {
    width: var(--sidebar-width);
    background: var(--bg-secondary);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    transition: var(--transition);
    position: relative;
}

.sidebar.collapsed {
    width: 80px;
}

.sidebar.collapsed .logo span,
.sidebar.collapsed .user-info,
.sidebar.collapsed .online-stats span,
.sidebar.collapsed .users-list h4,
.sidebar.collapsed .user-item span,
.sidebar.collapsed .version {
    display: none;
}

.sidebar.collapsed .user-profile {
    justify-content: center;
    padding: 16px 0;
}

.sidebar.collapsed .avatar i {
    font-size: 32px;
}

.sidebar-header {
    padding: 20px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    border-bottom: 1px solid var(--border-color);
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-weight: 600;
    font-size: 18px;
    color: var(--primary-color);
}

.logo i {
    font-size: 24px;
}

.sidebar-toggle {
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    width: 32px;
    height: 32px;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

.sidebar-toggle:hover {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.user-profile {
    padding: 20px;
    display: flex;
    align-items: center;
    gap: 12px;
    border-bottom: 1px solid var(--border-color);
}

.avatar i {
    font-size: 40px;
    color: var(--primary-color);
}

.user-info {
    flex: 1;
}

.username {
    font-weight: 600;
    color: var(--text-primary);
    display: block;
    margin-bottom: 4px;
}

.status {
    font-size: 12px;
    display: flex;
    align-items: center;
    gap: 4px;
}

.status i {
    font-size: 8px;
}

.status i.fa-circle {
    color: var(--success-color);
}

.online-stats {
    padding: 12px 20px;
    background: var(--bg-tertiary);
    margin: 0 20px 20px;
    border-radius: var(--border-radius);
    display: flex;
    align-items: center;
    gap: 8px;
    color: var(--text-secondary);
    font-size: 14px;
}

.online-stats i {
    color: var(--success-color);
}

.users-list {
    flex: 1;
    padding: 0 20px;
    overflow-y: auto;
}

.users-list h4 {
    color: var(--text-secondary);
    font-size: 12px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 12px;
}

.users-container {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.user-item {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 8px 12px;
    background: var(--bg-tertiary);
    border-radius: 10px;
    animation: slideIn 0.3s ease;
}

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

.user-item i {
    font-size: 8px;
}

.user-item span {
    font-size: 14px;
    color: var(--text-primary);
}

.loading-users {
    color: var(--text-tertiary);
    text-align: center;
    padding: 20px;
}

.sidebar-footer {
    padding: 20px;
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.theme-toggle {
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    width: 32px;
    height: 32px;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

.theme-toggle:hover {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.version {
    font-size: 12px;
    color: var(--text-tertiary);
}

/* Main Content */
.main-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    background: var(--bg-primary);
    position: relative;
}

.chat-header {
    height: var(--header-height);
    padding: 0 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    border-bottom: 1px solid var(--border-color);
    background: var(--bg-primary);
}

.header-left {
    display: flex;
    align-items: center;
    gap: 16px;
}

.mobile-menu-btn {
    display: none;
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 20px;
    cursor: pointer;
}

.header-left h2 {
    font-size: 18px;
    font-weight: 600;
    color: var(--text-primary);
}

.connection-badge {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 6px 12px;
    background: var(--bg-tertiary);
    border-radius: 20px;
    font-size: 13px;
}

.connection-badge i {
    font-size: 8px;
}

.connection-badge i.fa-circle {
    color: var(--success-color);
}

.messages-area {
    flex: 1;
    padding: 24px;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    gap: 16px;
    background: var(--bg-secondary);
}

.welcome-message {
    text-align: center;
    padding: 40px 20px;
    color: var(--text-tertiary);
}

.welcome-icon {
    font-size: 48px;
    color: var(--primary-color);
    margin-bottom: 16px;
    animation: bounce 2s infinite;
}

@keyframes bounce {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-10px); }
}

.welcome-message h3 {
    color: var(--text-primary);
    margin-bottom: 8px;
}

/* Message Bubbles */
.message {
    max-width: 60%;
    padding: 12px 16px;
    border-radius: 18px;
    animation: messagePop 0.3s ease;
    position: relative;
}

@keyframes messagePop {
    from {
        opacity: 0;
        transform: scale(0.8);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}

.message.own {
    align-self: flex-end;
    background: var(--primary-color);
    color: white;
    border-bottom-right-radius: 4px;
}

.message.other {
    align-self: flex-start;
    background: var(--bg-tertiary);
    color: var(--text-primary);
    border-bottom-left-radius: 4px;
}

.message.system {
    align-self: center;
    background: var(--bg-tertiary);
    color: var(--text-secondary);
    font-size: 12px;
    padding: 6px 12px;
    border-radius: 20px;
    max-width: 80%;
    opacity: 0.8;
}

.message-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 4px;
    font-size: 12px;
}

.message.own .message-header {
    color: rgba(255, 255, 255, 0.8);
}

.message.other .message-header {
    color: var(--text-secondary);
}

.message-user {
    font-weight: 600;
}

.message-time {
    font-size: 10px;
    margin-left: 8px;
}

.message-content {
    font-size: 14px;
    line-height: 1.5;
    word-wrap: break-word;
}

/* Typing Indicator */
.typing-indicator {
    padding: 8px 24px;
    color: var(--text-tertiary);
    font-size: 13px;
    font-style: italic;
    min-height: 36px;
    background: var(--bg-primary);
    border-top: 1px solid var(--border-color);
}

/* Input Area */
.input-footer {
    padding: 16px 24px;
    background: var(--bg-primary);
    border-top: 1px solid var(--border-color);
}

.message-form {
    display: flex;
    align-items: center;
    gap: 12px;
    background: var(--bg-tertiary);
    border-radius: 30px;
    padding: 4px 4px 4px 16px;
}

.emoji-btn {
    background: none;
    border: none;
    color: var(--text-tertiary);
    font-size: 20px;
    cursor: pointer;
    transition: var(--transition);
    padding: 8px;
}

.emoji-btn:hover {
    color: var(--primary-color);
    transform: scale(1.1);
}

#messageInput {
    flex: 1;
    background: none;
    border: none;
    padding: 12px 0;
    color: var(--text-primary);
    font-size: 14px;
    outline: none;
}

#messageInput::placeholder {
    color: var(--text-tertiary);
}

.send-btn {
    background: var(--primary-color);
    border: none;
    color: white;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
}

.send-btn:hover {
    background: var(--primary-dark);
    transform: scale(1.05);
}

.send-btn i {
    font-size: 18px;
}

/* Scroll to bottom button */
.scroll-bottom-btn {
    position: absolute;
    bottom: 100px;
    right: 24px;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: var(--primary-color);
    color: white;
    border: none;
    cursor: pointer;
    display: none;
    align-items: center;
    justify-content: center;
    box-shadow: var(--shadow-lg);
    transition: var(--transition);
    z-index: 10;
}

.scroll-bottom-btn:hover {
    background: var(--primary-dark);
    transform: scale(1.1);
}

.scroll-bottom-btn.visible {
    display: flex;
    animation: fadeIn 0.3s ease;
}

/* Emoji Picker */
.emoji-picker {
    position: absolute;
    bottom: 100px;
    left: 50%;
    transform: translateX(-50%);
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 20px;
    padding: 12px;
    box-shadow: var(--shadow-lg);
    display: none;
    z-index: 100;
}

.emoji-picker.show {
    display: block;
    animation: slideUp 0.3s ease;
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translate(-50%, 20px);
    }
    to {
        opacity: 1;
        transform: translate(-50%, 0);
    }
}

.emoji-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 8px;
}

.emoji-grid span {
    font-size: 24px;
    cursor: pointer;
    padding: 8px;
    border-radius: 8px;
    transition: var(--transition);
    text-align: center;
}

.emoji-grid span:hover {
    background: var(--bg-tertiary);
    transform: scale(1.2);
}

/* Responsive Design */
@media (max-width: 768px) {
    .app-container {
        height: 100vh;
        border-radius: 0;
    }

    .sidebar {
        position: absolute;
        left: -280px;
        height: 100%;
        z-index: 1000;
        box-shadow: var(--shadow-lg);
    }

    .sidebar.show {
        left: 0;
    }

    .mobile-menu-btn {
        display: block;
    }

    .message {
        max-width: 80%;
    }

    .emoji-picker {
        bottom: 80px;
        left: 10px;
        transform: none;
    }

    .emoji-picker.show {
        transform: none;
    }
}

/* Scrollbar */
::-webkit-scrollbar {
    width: 6px;
    height: 6px;
}

::-webkit-scrollbar-track {
    background: transparent;
}

::-webkit-scrollbar-thumb {
    background: var(--text-tertiary);
    border-radius: 3px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--text-secondary);
}

/* Animations */
@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.5; }
}

.loading {
    animation: pulse 1.5s ease-in-out infinite;
}

/* Glassmorphism Effect */
.glass {
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.2);
}

.dark-mode .glass {
    background: rgba(0, 0, 0, 0.2);
}