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

:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --danger-color: #dc2626;
    --danger-hover: #b91c1c;
    --bg-color: #f9fafb;
    --sidebar-bg: #ffffff;
    --border-color: #e5e7eb;
    --text-primary: #111827;
    --text-secondary: #6b7280;
    --message-user-bg: #2563eb;
    --message-ai-bg: #f3f4f6;
    --input-bg: #ffffff;
    --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.6;
}

.app-container {
    display: flex;
    height: 100vh;
    overflow: hidden;
}

.sidebar {
    width: 280px;
    background-color: var(--sidebar-bg);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
}

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

.sidebar-header h2 {
    font-size: 20px;
    font-weight: 600;
}

.conversations-list {
    flex: 1;
    overflow-y: auto;
    padding: 10px;
}

.conversation-item {
    padding: 12px;
    margin-bottom: 8px;
    border-radius: 8px;
    cursor: pointer;
    transition: background-color 0.2s;
}

.conversation-item:hover {
    background-color: var(--bg-color);
}

.conversation-item.active {
    background-color: var(--primary-color);
    color: white;
}

.conversation-item.active .conversation-meta {
    color: rgba(255, 255, 255, 0.8);
}

.conversation-title {
    font-weight: 500;
    margin-bottom: 4px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.conversation-meta {
    font-size: 12px;
    color: var(--text-secondary);
}

.sidebar-footer {
    padding: 20px;
    border-top: 1px solid var(--border-color);
}

.user-info {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.username {
    font-weight: 500;
}

.logout-link {
    color: var(--danger-color);
    text-decoration: none;
    font-size: 14px;
}

.logout-link:hover {
    text-decoration: underline;
}

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

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

.chat-header h3 {
    font-size: 18px;
    font-weight: 600;
}

.chat-actions {
    display: flex;
    gap: 10px;
}

.messages-container {
    flex: 1;
    overflow-y: auto;
    padding: 20px;
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.message {
    display: flex;
    gap: 12px;
    max-width: 80%;
    animation: fadeIn 0.3s ease-in;
}

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

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

.message-avatar {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 14px;
    flex-shrink: 0;
}

.message.user .message-avatar {
    background-color: var(--primary-color);
    color: white;
}

.message.assistant .message-avatar {
    background-color: var(--text-secondary);
    color: white;
}

.message-content {
    padding: 12px 16px;
    border-radius: 12px;
    word-wrap: break-word;
}

.message.user .message-content {
    background-color: var(--message-user-bg);
    color: white;
    border-bottom-right-radius: 4px;
}

.message.assistant .message-content {
    background-color: var(--message-ai-bg);
    color: var(--text-primary);
    border-bottom-left-radius: 4px;
}

.message-time {
    font-size: 11px;
    color: var(--text-secondary);
    margin-top: 4px;
}

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

.typing-indicator {
    display: flex;
    gap: 4px;
    padding: 12px 16px;
}

.typing-indicator span {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background-color: var(--text-secondary);
    animation: typing 1.4s infinite;
}

.typing-indicator span:nth-child(2) {
    animation-delay: 0.2s;
}

.typing-indicator span:nth-child(3) {
    animation-delay: 0.4s;
}

@keyframes typing {
    0%, 60%, 100% {
        transform: translateY(0);
        opacity: 0.5;
    }
    30% {
        transform: translateY(-10px);
        opacity: 1;
    }
}

.input-container {
    padding: 20px;
    background-color: var(--sidebar-bg);
    border-top: 1px solid var(--border-color);
}

#message-form {
    display: flex;
    gap: 12px;
    align-items: flex-end;
}

#message-input {
    flex: 1;
    padding: 12px 16px;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    font-family: inherit;
    font-size: 14px;
    resize: none;
    max-height: 120px;
    background-color: var(--input-bg);
}

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

.btn {
    padding: 10px 20px;
    border: none;
    border-radius: 8px;
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
}

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

.btn:active {
    transform: translateY(0);
}

.btn-primary {
    background-color: var(--primary-color);
    color: white;
}

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

.btn-danger {
    background-color: var(--danger-color);
    color: white;
}

.btn-danger:hover {
    background-color: var(--danger-hover);
}

.btn-small {
    padding: 6px 12px;
    font-size: 13px;
}

.btn-block {
    width: 100%;
}

.login-page {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

.login-container {
    width: 100%;
    max-width: 400px;
    padding: 20px;
}

.login-box {
    background-color: white;
    padding: 40px;
    border-radius: 12px;
    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.1);
}

.login-box h1 {
    text-align: center;
    margin-bottom: 8px;
    color: var(--primary-color);
}

.subtitle {
    text-align: center;
    color: var(--text-secondary);
    margin-bottom: 30px;
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 500;
    font-size: 14px;
}

.form-group input {
    width: 100%;
    padding: 12px;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    font-size: 14px;
    font-family: inherit;
}

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

.error-message {
    padding: 12px;
    background-color: #fee2e2;
    color: var(--danger-color);
    border-radius: 8px;
    margin-bottom: 20px;
    font-size: 14px;
}

.success-message {
    padding: 12px;
    background-color: #d1fae5;
    color: #065f46;
    border-radius: 8px;
    margin-bottom: 20px;
    font-size: 14px;
}

.register-link {
    text-align: center;
    margin-top: 20px;
    font-size: 14px;
    color: var(--text-secondary);
}

.register-link a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
}

.register-link a:hover {
    text-decoration: underline;
}

@media (max-width: 768px) {
    .sidebar {
        position: absolute;
        left: -280px;
        height: 100%;
        z-index: 100;
        transition: left 0.3s;
    }
    
    .sidebar.open {
        left: 0;
    }
    
    .message {
        max-width: 90%;
    }
}