/* ===========================
   Design System & CSS Variables
   =========================== */
:root {
  /* Colors - Dark Mode with Vibrant Accents */
  --bg-primary: #0a0e1a;
  --bg-secondary: #151b2e;
  --bg-tertiary: #1e2740;
  --bg-glass: rgba(30, 39, 64, 0.7);

  --accent-primary: #6366f1;
  --accent-secondary: #8b5cf6;
  --accent-gradient: linear-gradient(135deg, #6366f1 0%, #8b5cf6 100%);

  --text-primary: #f1f5f9;
  --text-secondary: #cbd5e1;
  --text-tertiary: #94a3b8;

  --border-color: rgba(148, 163, 184, 0.1);
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.5);

  /* Spacing */
  --spacing-xs: 0.5rem;
  --spacing-sm: 0.75rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;

  /* Typography */
  --font-family: "Inter", -apple-system, BlinkMacSystemFont, sans-serif;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 350ms ease;
}

/* ===========================
   Global Styles
   =========================== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: var(--font-family);
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  overflow: hidden;
}

a {
  color: var(--accent-primary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--accent-secondary);
}

/* ===========================
   App Container Layout
   =========================== */
.app-container {
  display: grid;
  grid-template-columns: 300px 1fr;
  height: 100vh;
  width: 100vw;
}

/* ===========================
   Sidebar - Conversation History
   =========================== */
.sidebar {
  background: var(--bg-secondary);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.sidebar-header {
  padding: var(--spacing-lg);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: var(--bg-glass);
  backdrop-filter: blur(10px);
}

.sidebar-header h1 {
  font-size: var(--font-size-xl);
  font-weight: 600;
}

.conversations-list {
  flex: 1;
  overflow-y: auto;
  padding: var(--spacing-md);
  display: flex;
  flex-direction: column;
  gap: var(--spacing-sm);
}

.conversation-item {
  padding: var(--spacing-md);
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  cursor: pointer;
  transition: all var(--transition-base);
}

.conversation-item:hover {
  background: var(--bg-glass);
  border-color: var(--accent-primary);
  transform: translateX(4px);
}

.conversation-item.active {
  background: var(--accent-gradient);
  border-color: var(--accent-primary);
  box-shadow: var(--shadow-md);
}

.conversation-title {
  font-weight: 500;
  margin-bottom: var(--spacing-xs);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.conversation-meta {
  font-size: var(--font-size-sm);
  color: var(--text-tertiary);
  display: flex;
  justify-content: space-between;
}

/* ===========================
   Chat Container
   =========================== */
.chat-container {
  display: flex;
  flex-direction: column;
  overflow: hidden;
  background: var(--bg-primary);
}

.chat-header {
  padding: var(--spacing-lg);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: var(--bg-glass);
  backdrop-filter: blur(10px);
}

.model-selector-container {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
}

.model-selector-container label {
  font-weight: 500;
  font-size: var(--font-size-lg);
}

.model-select {
  padding: var(--spacing-sm) var(--spacing-md);
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  color: var(--text-primary);
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  min-width: 300px;
  cursor: pointer;
  transition: all var(--transition-base);
}

.model-select:hover {
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.model-select:focus {
  outline: none;
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.2);
}

/* ===========================
   Messages Container
   =========================== */
.messages-container {
  flex: 1;
  overflow-y: auto;
  padding: var(--spacing-xl);
  display: flex;
  flex-direction: column;
  gap: var(--spacing-lg);
}

.welcome-screen {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 100%;
  text-align: center;
  gap: var(--spacing-xl);
}

.welcome-screen h2 {
  font-size: var(--font-size-2xl);
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.feature-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--spacing-lg);
  margin-top: var(--spacing-lg);
  max-width: 800px;
}

.feature-card {
  padding: var(--spacing-lg);
  background: var(--bg-glass);
  backdrop-filter: blur(10px);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  transition: all var(--transition-base);
}

.feature-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--accent-primary);
}

.feature-icon {
  font-size: 2.5rem;
  display: block;
  margin-bottom: var(--spacing-md);
}

.feature-card h3 {
  font-size: var(--font-size-lg);
  margin-bottom: var(--spacing-xs);
}

.feature-card p {
  color: var(--text-tertiary);
  font-size: var(--font-size-sm);
}

/* Message Bubbles */
.message {
  display: flex;
  gap: var(--spacing-md);
  animation: messageSlideIn var(--transition-base);
}

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

.message-avatar {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--font-size-lg);
  flex-shrink: 0;
}

.message.user .message-avatar {
  background: var(--accent-gradient);
}

.message.assistant .message-avatar {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
}

.message-content {
  flex: 1;
  padding: var(--spacing-md) var(--spacing-lg);
  background: var(--bg-glass);
  backdrop-filter: blur(10px);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  max-width: 80%;
}

.message.user .message-content {
  background: var(--accent-gradient);
}

.message-content pre {
  background: var(--bg-primary);
  padding: var(--spacing-md);
  border-radius: 8px;
  overflow-x: auto;
  margin: var(--spacing-sm) 0;
}

.message-content code {
  font-family: "Courier New", monospace;
  font-size: var(--font-size-sm);
}

.message-content p {
  margin-bottom: var(--spacing-sm);
}

.message-content p:last-child {
  margin-bottom: 0;
}

/* Loading indicator */
.typing-indicator {
  display: flex;
  gap: 4px;
  padding: var(--spacing-md);
}

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

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

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

@keyframes typingAnimation {
  0%,
  60%,
  100% {
    opacity: 0.3;
    transform: translateY(0);
  }
  30% {
    opacity: 1;
    transform: translateY(-10px);
  }
}

/* ===========================
   Input Container
   =========================== */
.input-container {
  padding: var(--spacing-lg);
  border-top: 1px solid var(--border-color);
  display: flex;
  gap: var(--spacing-md);
  background: var(--bg-glass);
  backdrop-filter: blur(10px);
}

#message-input {
  flex: 1;
  padding: var(--spacing-md) var(--spacing-lg);
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  color: var(--text-primary);
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  resize: none;
  max-height: 150px;
  transition: all var(--transition-base);
}

#message-input:focus {
  outline: none;
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.2);
}

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

/* ===========================
   Buttons
   =========================== */
.icon-btn {
  width: 40px;
  height: 40px;
  border: 1px solid var(--border-color);
  background: var(--bg-tertiary);
  color: var(--text-primary);
  border-radius: 10px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-base);
}

.icon-btn:hover {
  background: var(--accent-gradient);
  border-color: var(--accent-primary);
  transform: scale(1.05);
}

.send-btn {
  width: 50px;
  height: 50px;
  background: var(--accent-gradient);
  border: none;
  border-radius: 12px;
  color: white;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-base);
  box-shadow: var(--shadow-md);
}

.send-btn:hover {
  transform: scale(1.05);
  box-shadow: var(--shadow-lg);
}

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

.send-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

.primary-btn {
  padding: var(--spacing-md) var(--spacing-xl);
  background: var(--accent-gradient);
  border: none;
  border-radius: 10px;
  color: white;
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-base);
  box-shadow: var(--shadow-md);
}

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

/* ===========================
   Modal
   =========================== */
.modal {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.8);
  backdrop-filter: blur(5px);
  z-index: 1000;
  align-items: center;
  justify-content: center;
}

.modal.active {
  display: flex;
}

.modal-content {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 20px;
  padding: var(--spacing-xl);
  max-width: 500px;
  width: 90%;
  box-shadow: var(--shadow-lg);
  animation: modalSlideIn var(--transition-slow);
}

@keyframes modalSlideIn {
  from {
    opacity: 0;
    transform: scale(0.9) translateY(20px);
  }
  to {
    opacity: 1;
    transform: scale(1) translateY(0);
  }
}

.modal-content h2 {
  margin-bottom: var(--spacing-md);
  font-size: var(--font-size-2xl);
}

.modal-content p {
  color: var(--text-secondary);
  margin-bottom: var(--spacing-md);
}

.modal-content ol {
  margin: var(--spacing-md) 0;
  padding-left: var(--spacing-xl);
  color: var(--text-secondary);
}

.modal-content input {
  width: 100%;
  padding: var(--spacing-md);
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: 10px;
  color: var(--text-primary);
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  margin: var(--spacing-lg) 0;
}

.modal-content input:focus {
  outline: none;
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.2);
}

/* ===========================
   Scrollbar Styling
   =========================== */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: var(--bg-secondary);
}

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

::-webkit-scrollbar-thumb:hover {
  background: var(--accent-primary);
}

/* ===========================
   Mobile Menu Toggle Button
   =========================== */
.mobile-menu-toggle {
  display: none;
  width: 44px;
  height: 44px;
  border: 1px solid var(--border-color);
  background: var(--bg-tertiary);
  color: var(--text-primary);
  border-radius: 10px;
  cursor: pointer;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-base);
  flex-shrink: 0;
}

.mobile-menu-toggle:hover {
  background: var(--accent-gradient);
  border-color: var(--accent-primary);
}

.hamburger-icon {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.hamburger-icon span {
  width: 20px;
  height: 2px;
  background: var(--text-primary);
  border-radius: 2px;
  transition: all var(--transition-base);
}

/* Sidebar overlay for mobile */
.sidebar-overlay {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.6);
  backdrop-filter: blur(4px);
  z-index: 99;
  opacity: 0;
  transition: opacity var(--transition-base);
}

.sidebar-overlay.active {
  opacity: 1;
}

/* Close button for mobile sidebar */
.sidebar-close-btn {
  display: none;
  width: 36px;
  height: 36px;
  border: 1px solid var(--border-color);
  background: var(--bg-tertiary);
  color: var(--text-primary);
  border-radius: 8px;
  cursor: pointer;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-base);
}

.sidebar-close-btn:hover {
  background: #ef4444;
  border-color: #ef4444;
}

/* ===========================
   Responsive Design
   =========================== */

/* Tablet and small desktop */
@media (max-width: 1024px) {
  .app-container {
    grid-template-columns: 260px 1fr;
  }

  .model-select {
    min-width: 250px;
  }

  .feature-grid {
    grid-template-columns: repeat(3, 1fr);
    gap: var(--spacing-md);
  }
}

/* Mobile devices */
@media (max-width: 768px) {
  :root {
    --spacing-lg: 1.25rem;
    --spacing-xl: 1.5rem;
  }

  .app-container {
    grid-template-columns: 1fr;
    position: relative;
  }

  /* Mobile menu toggle visible */
  .mobile-menu-toggle {
    display: flex;
  }

  /* Sidebar becomes slide-out drawer */
  .sidebar {
    position: fixed;
    top: 0;
    left: 0;
    width: 85%;
    max-width: 320px;
    height: 100vh;
    z-index: 100;
    transform: translateX(-100%);
    transition: transform var(--transition-base);
    box-shadow: var(--shadow-lg);
  }

  .sidebar.open {
    transform: translateX(0);
  }

  .sidebar-overlay {
    display: block;
    pointer-events: none;
  }

  .sidebar-overlay.active {
    pointer-events: auto;
  }

  .sidebar-close-btn {
    display: flex;
  }

  .sidebar-header {
    padding: var(--spacing-md);
  }

  .sidebar-header h1 {
    font-size: var(--font-size-lg);
  }

  /* Chat header adjustments */
  .chat-header {
    padding: var(--spacing-md);
    flex-wrap: wrap;
    gap: var(--spacing-sm);
  }

  .model-selector-container {
    flex: 1;
    min-width: 0;
    gap: var(--spacing-sm);
  }

  .model-selector-container label {
    display: none;
  }

  .model-select {
    min-width: 0;
    width: 100%;
    font-size: var(--font-size-sm);
    padding: var(--spacing-sm);
  }

  .header-actions {
    display: flex;
    gap: var(--spacing-sm);
  }

  /* Feature grid single column */
  .feature-grid {
    grid-template-columns: 1fr;
    gap: var(--spacing-md);
    padding: 0 var(--spacing-md);
    max-width: 100%;
  }

  .feature-card {
    padding: var(--spacing-md);
    border-radius: 12px;
  }

  .feature-icon {
    font-size: 2rem;
    margin-bottom: var(--spacing-sm);
  }

  .feature-card h3 {
    font-size: var(--font-size-base);
  }

  /* Welcome screen */
  .welcome-screen {
    padding: var(--spacing-md);
    gap: var(--spacing-lg);
  }

  .welcome-screen h2 {
    font-size: var(--font-size-xl);
    line-height: 1.3;
  }

  .welcome-screen > p {
    font-size: var(--font-size-sm);
    padding: 0 var(--spacing-md);
  }

  /* Messages area */
  .messages-container {
    padding: var(--spacing-md);
    gap: var(--spacing-md);
  }

  .message {
    gap: var(--spacing-sm);
  }

  .message-avatar {
    width: 32px;
    height: 32px;
    font-size: var(--font-size-sm);
  }

  .message-content {
    max-width: calc(100% - 44px);
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: 12px;
    font-size: var(--font-size-sm);
  }

  .message-content pre {
    padding: var(--spacing-sm);
    font-size: 0.75rem;
  }

  /* Input area */
  .input-container {
    padding: var(--spacing-md);
    gap: var(--spacing-sm);
  }

  #message-input {
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: var(--font-size-base);
    border-radius: 10px;
  }

  .send-btn {
    width: 44px;
    height: 44px;
    border-radius: 10px;
    flex-shrink: 0;
  }

  .send-btn svg {
    width: 20px;
    height: 20px;
  }

  /* Buttons - larger touch targets */
  .icon-btn {
    width: 44px;
    height: 44px;
  }

  /* Modal adjustments */
  .modal-content {
    padding: var(--spacing-lg);
    margin: var(--spacing-md);
    border-radius: 16px;
    max-height: 90vh;
    overflow-y: auto;
  }

  .modal-content h2 {
    font-size: var(--font-size-xl);
  }

  .modal-content ol {
    padding-left: var(--spacing-lg);
  }

  .primary-btn {
    width: 100%;
    padding: var(--spacing-md);
  }
}

/* Small mobile devices */
@media (max-width: 480px) {
  :root {
    --spacing-md: 0.875rem;
    --spacing-lg: 1rem;
  }

  .sidebar {
    width: 100%;
    max-width: none;
  }

  .chat-header {
    padding: var(--spacing-sm) var(--spacing-md);
  }

  .model-select {
    padding: 10px var(--spacing-sm);
  }

  .welcome-screen h2 {
    font-size: var(--font-size-lg);
  }

  .feature-card {
    padding: var(--spacing-sm) var(--spacing-md);
  }

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

  .feature-card h3 {
    font-size: var(--font-size-sm);
  }

  .feature-card p {
    font-size: 0.75rem;
  }

  .message-avatar {
    width: 28px;
    height: 28px;
    font-size: 0.75rem;
  }

  .message-content {
    max-width: calc(100% - 36px);
    padding: var(--spacing-sm);
  }

  .input-container {
    padding: var(--spacing-sm) var(--spacing-md);
  }

  #message-input {
    padding: var(--spacing-sm);
    font-size: var(--font-size-sm);
  }

  .send-btn {
    width: 40px;
    height: 40px;
  }

  .modal-content {
    padding: var(--spacing-md);
    margin: var(--spacing-sm);
  }
}

/* Landscape mobile */
@media (max-height: 500px) and (orientation: landscape) {
  .welcome-screen {
    padding: var(--spacing-sm);
    gap: var(--spacing-sm);
  }

  .feature-grid {
    grid-template-columns: repeat(3, 1fr);
    gap: var(--spacing-sm);
  }

  .feature-card {
    padding: var(--spacing-sm);
  }

  .feature-icon {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-xs);
  }

  .messages-container {
    padding: var(--spacing-sm) var(--spacing-md);
  }
}