:root {
    /* Color Palette - Light Mode */
    --bg-primary: #f8fafc;
    --bg-secondary: #ffffff;
    --bg-tertiary: #f1f5f9;
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-tertiary: #94a3b8;
    
    /* Accent Colors */
    --accent-primary: #667eea;
    --accent-secondary: #764ba2;
    --accent-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --accent-gradient-hover: linear-gradient(135deg, #5568d3 0%, #6a4391 100%);
    
    /* Message Colors */
    --msg-user-bg: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --msg-user-text: #ffffff;
    --msg-ai-bg: #f1f5f9;
    --msg-ai-text: #0f172a;
    
    /* Status Colors */
    --success: #10b981;
    --error: #ef4444;
    --warning: #f59e0b;
    
    /* Shadows & Effects */
    --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);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
    
    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    
    /* Transitions */
    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 350ms cubic-bezier(0.4, 0, 0.2, 1);
}

[data-theme="dark"] {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --text-primary: #f1f5f9;
    --text-secondary: #cbd5e1;
    --text-tertiary: #64748b;
    
    --msg-ai-bg: #1e293b;
    --msg-ai-text: #f1f5f9;
    
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.5);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.6);
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    transition: background-color var(--transition-base), color var(--transition-base);
    overflow: hidden;
}

.app-container {
    display: flex;
    flex-direction: column;
    height: 100vh;
    max-width: 1400px;
    margin: 0 auto;
}

/* Header Styles */
.header {
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--bg-tertiary);
    padding: 1rem 1.5rem;
    backdrop-filter: blur(10px);
    box-shadow: var(--shadow-sm);
    z-index: 10;
}

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

.logo-section {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.logo-icon {
    animation: float 3s ease-in-out infinite;
}

@keyframes float {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-5px); }
}

.logo-text h1 {
    font-size: 1.25rem;
    font-weight: 700;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.logo-text p {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-top: -2px;
}

.header-actions {
    display: flex;
    gap: 0.5rem;
}

.btn-icon {
    width: 40px;
    height: 40px;
    border: none;
    border-radius: var(--radius-md);
    background: var(--bg-tertiary);
    color: var(--text-primary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
    position: relative;
    overflow: hidden;
}

.btn-icon::before {
    content: '';
    position: absolute;
    inset: 0;
    background: var(--accent-gradient);
    opacity: 0;
    transition: opacity var(--transition-fast);
}

.btn-icon:hover::before {
    opacity: 0.1;
}

.btn-icon:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

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

.btn-icon svg {
    position: relative;
    z-index: 1;
}

.theme-icon {
    transition: opacity var(--transition-fast);
}

[data-theme="light"] .moon {
    opacity: 0;
    position: absolute;
}

[data-theme="dark"] .sun {
    opacity: 0;
    position: absolute;
}

/* Chat Container */
.chat-container {
    flex: 1;
    overflow-y: auto;
    padding: 2rem 1.5rem;
    scroll-behavior: smooth;
}

.chat-container::-webkit-scrollbar {
    width: 8px;
}

.chat-container::-webkit-scrollbar-track {
    background: transparent;
}

.chat-container::-webkit-scrollbar-thumb {
    background: var(--bg-tertiary);
    border-radius: 4px;
}

.chat-container::-webkit-scrollbar-thumb:hover {
    background: var(--text-tertiary);
}

.chat-messages {
    max-width: 900px;
    margin: 0 auto;
}

/* Welcome Message */
.welcome-message {
    text-align: center;
    padding: 3rem 2rem;
    animation: fadeInUp 0.6s ease-out;
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.welcome-icon {
    font-size: 4rem;
    margin-bottom: 1rem;
    animation: bounce 2s ease-in-out infinite;
}

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

.welcome-message h2 {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 1rem;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.welcome-message > p {
    color: var(--text-secondary);
    font-size: 1.125rem;
    margin-bottom: 2rem;
}

.suggestion-chips {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
    justify-content: center;
    margin-bottom: 2rem;
}

.chip {
    padding: 0.75rem 1.5rem;
    border: 2px solid var(--bg-tertiary);
    border-radius: var(--radius-xl);
    background: var(--bg-secondary);
    color: var(--text-primary);
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-fast);
    box-shadow: var(--shadow-sm);
}

.chip:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
    border-color: var(--accent-primary);
    background: var(--accent-gradient);
    color: white;
}

.hint {
    color: var(--text-tertiary);
    font-size: 0.875rem;
    font-style: italic;
}

/* Message Styles */
.message {
    display: flex;
    margin-bottom: 1.5rem;
    animation: messageSlideIn 0.3s ease-out;
}

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

.message.user {
    justify-content: flex-end;
}

.message.ai {
    justify-content: flex-start;
}

.message-content {
    max-width: 75%;
    padding: 1rem 1.25rem;
    border-radius: var(--radius-lg);
    position: relative;
    word-wrap: break-word;
}

.message.user .message-content {
    background: var(--msg-user-bg);
    color: var(--msg-user-text);
    border-bottom-right-radius: 4px;
    box-shadow: var(--shadow-md);
}

.message.ai .message-content {
    background: var(--msg-ai-bg);
    color: var(--msg-ai-text);
    border-bottom-left-radius: 4px;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--bg-tertiary);
}

.message-text {
    font-size: 0.9375rem;
    line-height: 1.6;
}

.message-time {
    font-size: 0.75rem;
    opacity: 0.7;
    margin-top: 0.5rem;
    display: block;
}

/* Typing Indicator */
.typing-indicator {
    display: flex;
    align-items: center;
    padding: 1rem 1.25rem;
    background: var(--msg-ai-bg);
    border-radius: var(--radius-lg);
    border-bottom-left-radius: 4px;
    max-width: 75px;
    margin-bottom: 1.5rem;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--bg-tertiary);
}

.typing-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: var(--text-tertiary);
    margin: 0 3px;
    animation: typingDot 1.4s infinite;
}

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

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

@keyframes typingDot {
    0%, 60%, 100% {
        transform: translateY(0);
        opacity: 0.7;
    }
    30% {
        transform: translateY(-10px);
        opacity: 1;
    }
}

/* Input Container */
.input-container {
    background: var(--bg-secondary);
    border-top: 1px solid var(--bg-tertiary);
    padding: 1.5rem;
    box-shadow: var(--shadow-lg);
}

.input-wrapper {
    max-width: 900px;
    margin: 0 auto;
    display: flex;
    gap: 0.75rem;
    align-items: flex-end;
}

#messageInput {
    flex: 1;
    padding: 1rem 1.25rem;
    border: 2px solid var(--bg-tertiary);
    border-radius: var(--radius-lg);
    background: var(--bg-primary);
    color: var(--text-primary);
    font-family: inherit;
    font-size: 0.9375rem;
    resize: none;
    max-height: 120px;
    transition: all var(--transition-fast);
    outline: none;
}

#messageInput:focus {
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

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

.btn-send {
    width: 48px;
    height: 48px;
    border: none;
    border-radius: var(--radius-md);
    background: var(--accent-gradient);
    color: white;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
    box-shadow: var(--shadow-md);
}

.btn-send:hover:not(:disabled) {
    background: var(--accent-gradient-hover);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-send:active:not(:disabled) {
    transform: translateY(0);
}

.btn-send:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.input-footer {
    max-width: 900px;
    margin: 0.75rem auto 0;
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.75rem;
    color: var(--text-tertiary);
}

.status-indicator {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.status-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: var(--success);
    animation: pulse 2s ease-in-out infinite;
}

@keyframes pulse {
    0%, 100% {
        opacity: 1;
        transform: scale(1);
    }
    50% {
        opacity: 0.7;
        transform: scale(0.95);
    }
}

.status-indicator.error .status-dot {
    background: var(--error);
}

.char-count {
    font-variant-numeric: tabular-nums;
}

/* Toast Notifications */
.toast {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    background: var(--bg-secondary);
    color: var(--text-primary);
    padding: 1rem 1.5rem;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-xl);
    border: 1px solid var(--bg-tertiary);
    z-index: 1000;
    animation: slideInRight 0.3s ease-out;
}

@keyframes slideInRight {
    from {
        opacity: 0;
        transform: translateX(100%);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.toast.success {
    border-left: 4px solid var(--success);
}

.toast.error {
    border-left: 4px solid var(--error);
}

/* Responsive Design */
@media (max-width: 768px) {
    .header {
        padding: 1rem;
    }

    .logo-text h1 {
        font-size: 1.125rem;
    }

    .logo-text p {
        font-size: 0.75rem;
    }

    .chat-container {
        padding: 1rem;
    }

    .welcome-message {
        padding: 2rem 1rem;
    }

    .welcome-message h2 {
        font-size: 1.5rem;
    }

    .welcome-icon {
        font-size: 3rem;
    }

    .suggestion-chips {
        flex-direction: column;
    }

    .chip {
        width: 100%;
    }

    .message-content {
        max-width: 85%;
    }

    .input-container {
        padding: 1rem;
    }

    .toast {
        right: 1rem;
        left: 1rem;
        bottom: 1rem;
    }
}

/* Loading Animation */
@keyframes shimmer {
    0% {
        background-position: -1000px 0;
    }
    100% {
        background-position: 1000px 0;
    }
}

.loading {
    background: linear-gradient(
        90deg,
        var(--bg-tertiary) 0%,
        var(--bg-secondary) 50%,
        var(--bg-tertiary) 100%
    );
    background-size: 1000px 100%;
    animation: shimmer 2s infinite linear;
}