:root {
    --primary-color: #6366f1;
    --primary-hover: #5558e3;
    --bg-primary: #ffffff;
    --bg-secondary: #f9fafb;
    --bg-tertiary: #f3f4f6;
    --text-primary: #111827;
    --text-secondary: #6b7280;
    --text-tertiary: #9ca3af;
    --border-color: #e5e7eb;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 14px;
    --transition: all 0.2s ease;
}

[data-theme="dark"] {
    --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;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: var(--bg-secondary);
    color: var(--text-primary);
    overflow: hidden;
    height: 100vh;
}

.screen {
    display: none;
    height: 100vh;
}

.screen.active {
    display: flex;
}

#login-screen {
    justify-content: center;
    align-items: center;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

.login-container {
    background: var(--bg-primary);
    padding: 3rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    max-width: 450px;
    width: 90%;
    text-align: center;
}

.logo {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
    margin-bottom: 1rem;
}

.logo h1 {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-primary);
}

.tagline {
    color: var(--text-secondary);
    margin-bottom: 2rem;
    font-size: 0.95rem;
}

.login-form {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    margin-bottom: 2rem;
}

.login-form input {
    padding: 0.875rem 1rem;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
    transition: var(--transition);
    background: var(--bg-secondary);
    color: var(--text-primary);
}

.login-form input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.primary-btn {
    padding: 0.875rem 1.5rem;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: var(--radius-md);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
}

.primary-btn:hover {
    background: var(--primary-hover);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.features {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1rem;
    margin-top: 2rem;
}

.feature {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
    padding: 1rem;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.feature .icon {
    font-size: 1.5rem;
}

.app-container {
    display: flex;
    height: 100vh;
    background: var(--bg-primary);
}

.sidebar {
    width: 320px;
    background: var(--bg-secondary);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
}

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

.user-profile {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.avatar {
    width: 42px;
    height: 42px;
    border-radius: 50%;
    background: var(--primary-color);
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 1.125rem;
}

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

.username {
    font-weight: 600;
    font-size: 0.95rem;
    color: var(--text-primary);
}

.status-select {
    background: transparent;
    border: none;
    color: var(--text-secondary);
    font-size: 0.8rem;
    cursor: pointer;
    padding: 0;
}

.icon-btn {
    width: 36px;
    height: 36px;
    border-radius: var(--radius-sm);
    border: none;
    background: transparent;
    color: var(--text-secondary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
    font-size: 1.2rem;
}

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

.sidebar-tabs {
    display: flex;
    border-bottom: 1px solid var(--border-color);
}

.tab-btn {
    flex: 1;
    padding: 0.875rem;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    cursor: pointer;
    font-size: 0.875rem;
    font-weight: 500;
    transition: var(--transition);
    border-bottom: 2px solid transparent;
}

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

.tab-btn.active {
    color: var(--primary-color);
    border-bottom-color: var(--primary-color);
}

.sidebar-content {
    flex: 1;
    overflow-y: auto;
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
}

.search-bar {
    padding: 1rem;
    display: flex;
    align-items: center;
    gap: 0.75rem;
    border-bottom: 1px solid var(--border-color);
    background: var(--bg-primary);
}

.search-bar input {
    flex: 1;
    border: none;
    background: transparent;
    color: var(--text-primary);
    font-size: 0.9rem;
}

.search-bar input:focus {
    outline: none;
}

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

.list-header h3 {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
}

.list {
    padding: 0.5rem 0;
}

.user-item, .conversation-item, .room-item {
    padding: 0.875rem 1rem;
    display: flex;
    align-items: center;
    gap: 0.875rem;
    cursor: pointer;
    transition: var(--transition);
}

.user-item:hover, .conversation-item:hover, .room-item:hover {
    background: var(--bg-tertiary);
}

.item-info {
    flex: 1;
    min-width: 0;
}

.item-name {
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--text-primary);
}

.item-message {
    font-size: 0.825rem;
    color: var(--text-secondary);
}

.chat-area {
    flex: 1;
    display: flex;
    flex-direction: column;
    background: var(--bg-primary);
}

.welcome-screen {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
}

.welcome-content {
    text-align: center;
    max-width: 500px;
}

.welcome-content h2 {
    font-size: 1.75rem;
    margin: 1.5rem 0 0.75rem;
}

.chat-container {
    flex: 1;
    display: flex;
    flex-direction: column;
    height: 100%;
}

.chat-header {
    padding: 1rem 1.5rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: var(--bg-secondary);
}

.chat-info {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.chat-info h3 {
    font-size: 1rem;
    font-weight: 600;
}

.chat-status {
    font-size: 0.8rem;
    color: var(--text-secondary);
}

.messages-container {
    flex: 1;
    overflow-y: auto;
    padding: 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.message {
    display: flex;
    gap: 0.75rem;
    max-width: 70%;
}

.message.own {
    align-self: flex-end;
    flex-direction: row-reverse;
}

.message-content {
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.message-header {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.message-author {
    font-size: 0.825rem;
    font-weight: 600;
}

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

.message-bubble {
    padding: 0.75rem 1rem;
    border-radius: var(--radius-md);
    background: var(--bg-secondary);
    color: var(--text-primary);
}

.message.own .message-bubble {
    background: var(--primary-color);
    color: white;
}

.message-input-container {
    padding: 1rem 1.5rem;
    border-top: 1px solid var(--border-color);
    display: flex;
    align-items: flex-end;
    gap: 0.75rem;
    background: var(--bg-secondary);
}

.message-input {
    flex: 1;
    min-height: 44px;
    max-height: 150px;
    padding: 0.75rem 1rem;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    background: var(--bg-primary);
    color: var(--text-primary);
    overflow-y: auto;
}

.message-input:focus {
    outline: none;
    border-color: var(--primary-color);
}

.message-input:empty::before {
    content: attr(placeholder);
    color: var(--text-tertiary);
}

.send-btn {
    width: 44px;
    height: 44px;
    border-radius: 50%;
    border: none;
    background: var(--primary-color);
    color: white;
    cursor: pointer;
    font-size: 1.2rem;
    transition: var(--transition);
}

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

.emoji-picker {
    position: absolute;
    bottom: 80px;
    left: 20px;
    width: 320px;
    height: 350px;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    z-index: 100;
}

.emoji-grid {
    padding: 1rem;
    display: grid;
    grid-template-columns: repeat(8, 1fr);
    gap: 0.5rem;
    overflow-y: auto;
    height: 100%;
}

.emoji-grid button {
    width: 32px;
    height: 32px;
    border: none;
    background: transparent;
    font-size: 1.5rem;
    cursor: pointer;
    border-radius: var(--radius-sm);
    transition: var(--transition);
}

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

.encryption-active {
    background: rgba(99, 102, 241, 0.1);
    color: var(--primary-color);
}

.typing-indicator {
    padding: 0.5rem 1.5rem;
    font-size: 0.825rem;
    color: var(--text-secondary);
}