/* 
 * Performance-Optimized CSS
 * Minimal repaints, GPU-accelerated animations, efficient selectors
 */

/* CSS Variables for theming */
:root {
    --primary: #2563eb;
    --primary-dark: #1e40af;
    --bg: #f8fafc;
    --surface: #ffffff;
    --text: #1e293b;
    --text-light: #64748b;
    --border: #e2e8f0;
    --user-bubble: #2563eb;
    --bot-bubble: #f1f5f9;
    --warning-bg: #fef3c7;
    --warning-border: #f59e0b;
    --warning-text: #92400e;
}

/* Reset */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

/* Base */
body {
    font-family: 'Work Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    line-height: 1.5;
    color: var(--text);
    background: var(--bg);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Performance Warning Banner */
.performance-warning {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    padding: 12px 20px;
    background: var(--warning-bg);
    border-bottom: 2px solid var(--warning-border);
    color: var(--warning-text);
    font-size: 14px;
    text-align: center;
    will-change: transform;
    transform: translateZ(0); /* GPU acceleration */
}

.performance-warning a {
    color: var(--primary);
    font-weight: 600;
    text-decoration: underline;
}

.performance-warning.hidden {
    display: none;
}

/* Main Container - Mobile Size Only */
.container {
    max-width: 375px;
    max-height: 720px;
    width: 100%;
    height: 100vh;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    background: var(--surface);
    box-shadow: 0 0 0 1px rgba(0,0,0,0.05);
}

/* Header */
.header {
    flex-shrink: 0;
    padding: 12px 12px;
    background: var(--primary);
    color: white;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
}

.header h1 {
    font-family: 'Young Serif', serif;
    font-size: 20px;
    font-weight: 400;
}

.header-actions {
    display: flex;
    gap: 10px;
    align-items: center;
}

/* AI Toggle Switch */
.ai-toggle {
    display: flex;
    align-items: center;
    gap: 8px;
    cursor: pointer;
}

.ai-toggle input {
    display: none;
}

.toggle-slider {
    position: relative;
    width: 40px;
    height: 22px;
    background: rgba(255, 255, 255, 0.3);
    border-radius: 11px;
    transition: background 0.2s ease;
}

.toggle-slider::before {
    content: '';
    position: absolute;
    width: 18px;
    height: 18px;
    border-radius: 50%;
    background: white;
    top: 2px;
    left: 2px;
    transition: transform 0.2s ease;
}

.ai-toggle input:checked + .toggle-slider {
    background: rgba(255, 255, 255, 0.5);
}

.ai-toggle input:checked + .toggle-slider::before {
    transform: translateX(18px);
}

.toggle-label {
    font-size: 13px;
    font-weight: 500;
    color: white;
}

/* Menu Button */
.menu-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    background: rgba(255, 255, 255, 0.15);
    border: none;
    border-radius: 6px;
    color: white;
    cursor: pointer;
    transition: background 0.15s ease;
}

.menu-btn:hover {
    background: rgba(255, 255, 255, 0.25);
}

/* Chat Container */
.chat-container {
    flex: 1;
    display: flex;
    flex-direction: column;
    min-height: 0; /* Important for flex scrolling */
}

/* Messages Wrapper */
.messages-wrapper {
    flex: 1;
    overflow-y: auto;
    overflow-x: hidden;
    padding: 12px;
    scroll-behavior: smooth;
    /* Optimize scrolling performance */
    will-change: scroll-position;
    -webkit-overflow-scrolling: touch;
}

.messages {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

/* Messages */
.message {
    display: flex;
    animation: messageSlide 0.2s ease-out;
    /* Use GPU for animation */
    will-change: transform, opacity;
    transform: translateZ(0);
}

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

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

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

.message-bubble {
    max-width: 75%;
    padding: 10px 16px;
    border-radius: 16px;
    word-wrap: break-word;
    font-size: 15px;
    line-height: 1.4;
}

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

.message.bot .message-bubble {
    background: var(--bot-bubble);
    color: var(--text);
    border-bottom-left-radius: 4px;
}

/* Typing Indicator */
.typing-indicator {
    display: flex;
    gap: 4px;
    padding: 4px;
}

.typing-indicator span {
    width: 8px;
    height: 8px;
    background: var(--text-light);
    border-radius: 50%;
    animation: typingBounce 1.4s infinite ease-in-out;
    will-change: transform;
    transform: translateZ(0);
}

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

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

@keyframes typingBounce {
    0%, 60%, 100% {
        transform: translateY(0) translateZ(0);
        opacity: 0.6;
    }
    30% {
        transform: translateY(-8px) translateZ(0);
        opacity: 1;
    }
}

/* Input Container */
.input-container {
    flex-shrink: 0;
    padding: 12px 12px;
    border-top: 1px solid var(--border);
    background: var(--surface);
    display: flex;
    gap: 8px;
    align-items: flex-end;
}

.menu-btn-bottom {
    flex-shrink: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 6px;
    color: var(--text);
    cursor: pointer;
    transition: background 0.15s ease;
}

.menu-btn-bottom:hover {
    background: var(--border);
}

.user-input {
    flex: 1;
    min-height: 44px;
    max-height: 120px;
    padding: 12px 16px;
    border: 1px solid var(--border);
    border-radius: 22px;
    font-family: inherit;
    font-size: 15px;
    line-height: 1.4;
    resize: none;
    outline: none;
    transition: border-color 0.15s ease;
    overflow-y: auto;
}

.user-input:focus {
    border-color: var(--primary);
}

.send-btn {
    flex-shrink: 0;
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--primary);
    color: white;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    transition: background 0.15s ease, transform 0.1s ease;
    /* GPU acceleration */
    will-change: transform;
    transform: translateZ(0);
}

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

.send-btn:active {
    transform: scale(0.95) translateZ(0);
}

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

/* Footer */
.footer {
    flex-shrink: 0;
    padding: 12px 12px;
    border-top: 1px solid var(--border);
    text-align: center;
    font-size: 13px;
    color: var(--text-light);
}

.footer a {
    color: var(--primary);
    text-decoration: none;
}

.footer a:hover {
    text-decoration: underline;
}

/* Side Drawer */
.drawer {
    position: fixed;
    top: 0;
    right: -300px;
    width: 280px;
    height: 100vh;
    background: var(--surface);
    box-shadow: -2px 0 10px rgba(0,0,0,0.1);
    transition: right 0.3s ease;
    z-index: 1001;
    overflow-y: auto;
}

.drawer.open {
    right: 0;
}

.drawer-content {
    padding: 20px;
}

.close-drawer {
    position: absolute;
    top: 12px;
    right: 12px;
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: none;
    border: none;
    font-size: 28px;
    color: var(--text);
    cursor: pointer;
    line-height: 1;
}

.drawer h2 {
    font-family: 'Young Serif', serif;
    font-size: 24px;
    font-weight: 400;
    margin-bottom: 12px;
    color: var(--text);
}

.drawer h3 {
    font-size: 16px;
    font-weight: 600;
    margin: 20px 0 8px;
    color: var(--text);
}

.drawer p {
    font-size: 14px;
    line-height: 1.6;
    margin-bottom: 12px;
    color: var(--text);
}

.drawer ul {
    margin: 0 0 12px 20px;
    font-size: 14px;
}

.drawer li {
    margin-bottom: 6px;
    color: var(--text);
}

.drawer-btn {
    display: block;
    width: 100%;
    padding: 10px 16px;
    margin-bottom: 10px;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 8px;
    font-family: inherit;
    font-size: 14px;
    font-weight: 500;
    color: var(--text);
    cursor: pointer;
    transition: all 0.15s ease;
}

.drawer-btn:hover {
    background: var(--border);
}

.drawer-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s ease;
    z-index: 1000;
}

.drawer-overlay.visible {
    opacity: 1;
    visibility: visible;
}

/* Utility */
.hidden {
    display: none !important;
}

/* Scrollbar Styling */
.messages-wrapper::-webkit-scrollbar {
    width: 8px;
}

.messages-wrapper::-webkit-scrollbar-track {
    background: transparent;
}

.messages-wrapper::-webkit-scrollbar-thumb {
    background: var(--border);
    border-radius: 4px;
}

.messages-wrapper::-webkit-scrollbar-thumb:hover {
    background: var(--text-light);
}

/* Reduced Motion */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}