:root {
  --primary: #4f46e5;
  --primary-hover: #4338ca;
  --primary-light: #eef2ff;
  --bg: #f8fafc;
  --surface: #ffffff;
  --text-primary: #0f172a;
  --text-secondary: #64748b;
  --text-muted: #94a3b8;
  --border: #e2e8f0;
  --shadow: 0 1px 3px 0 rgb(0 0 0 / 0.1), 0 1px 2px -1px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
  --radius: 12px;
  --radius-sm: 8px;
}

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

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background-color: var(--bg);
  color: var(--text-primary);
  line-height: 1.5;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* App Container */
.app-container {
  flex: 1;
  display: flex;
  flex-direction: column;
  max-width: 800px;
  width: 100%;
  margin: 0 auto;
  background: var(--surface);
  box-shadow: var(--shadow-lg);
  min-height: 100vh;
}

/* Header */
.app-header {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 1rem 1.5rem;
  position: sticky;
  top: 0;
  z-index: 10;
}

.header-content {
  max-width: 100%;
  margin: 0 auto;
}

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

.logo {
  width: 40px;
  height: 40px;
  background: var(--primary-light);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--primary);
  font-size: 1.25rem;
}

.brand-text h1 {
  font-size: 1.125rem;
  font-weight: 600;
  color: var(--text-primary);
  line-height: 1.25;
}

.status {
  font-size: 0.75rem;
  color: #10b981;
  font-weight: 500;
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

.status::before {
  content: '';
  width: 6px;
  height: 6px;
  background: #10b981;
  border-radius: 50%;
  display: inline-block;
}

/* Chat Container */
.chat-container {
  flex: 1;
  overflow: hidden;
  display: flex;
  flex-direction: column;
  background: var(--bg);
}

.messages-wrapper {
  flex: 1;
  overflow-y: auto;
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  gap: 1rem;
  scroll-behavior: smooth;
}

.messages-wrapper::-webkit-scrollbar {
  width: 6px;
}

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

.messages-wrapper::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 3px;
}

/* Empty State */
.empty-state {
  text-align: center;
  padding: 3rem 1rem;
  color: var(--text-secondary);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
}

.empty-state.hidden {
  display: none;
}

.empty-icon {
  width: 64px;
  height: 64px;
  background: var(--surface);
  border: 2px solid var(--border);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  color: var(--text-muted);
}

.empty-state h3 {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
}

.empty-state p {
  font-size: 0.875rem;
  max-width: 300px;
  line-height: 1.5;
}

/* Messages */
.msg {
  max-width: 75%;
  padding: 0.875rem 1rem;
  border-radius: var(--radius);
  font-size: 0.9375rem;
  line-height: 1.5;
  word-wrap: break-word;
  position: relative;
  animation: messageSlide 0.3s ease-out;
}

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

.msg.other {
  background: var(--surface);
  color: var(--text-primary);
  border: 1px solid var(--border);
  border-bottom-left-radius: 4px;
  align-self: flex-start;
  box-shadow: var(--shadow);
}

.msg.user {
  background: var(--primary);
  color: white;
  border-bottom-right-radius: 4px;
  align-self: flex-end;
}

/* Footer */
.chat-footer {
  background: var(--surface);
  border-top: 1px solid var(--border);
  padding: 1rem 1.5rem 1.25rem;
}

.input-container {
  display: flex;
  align-items: flex-end;
  gap: 0.75rem;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 24px;
  padding: 0.5rem 0.5rem 0.5rem 1rem;
  transition: all 0.2s;
}

.input-container:focus-within {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-light);
}

.message-input {
  flex: 1;
  background: transparent;
  border: none;
  outline: none;
  resize: none;
  font-family: inherit;
  font-size: 16px;
  line-height: 1.5;
  max-height: 120px;
  min-height: 24px;
  padding: 0.25rem 0;
  color: var(--text-primary);
}

.message-input::placeholder {
  color: var(--text-muted);
}

.send-button {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: var(--primary);
  color: white;
  border: none;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all 0.2s;
  flex-shrink: 0;
}

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

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

.input-hint {
  text-align: center;
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-top: 0.5rem;
}

/* Upload Section */
.upload-section {
  padding: 2rem 1rem;
  background: var(--bg);
}

.upload-card {
  max-width: 600px;
  margin: 0 auto;
  background: var(--surface);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 2rem;
  border: 1px solid var(--border);
}

.upload-header {
  text-align: center;
  margin-bottom: 1.5rem;
}

.upload-header i {
  font-size: 2.5rem;
  color: var(--primary);
  margin-bottom: 0.5rem;
  display: block;
}

.upload-header h2 {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: 0.25rem;
  color: var(--text-primary);
}

.upload-header p {
  font-size: 0.875rem;
  color: var(--text-secondary);
}

.upload-form {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.file-inputs {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.file-input-wrapper {
  position: relative;
}

.file-input {
  position: absolute;
  opacity: 0;
  width: 100%;
  height: 100%;
  cursor: pointer;
}

.file-label {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.875rem 1rem;
  border: 2px dashed var(--border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all 0.2s;
  color: var(--text-secondary);
  font-size: 0.875rem;
}

.file-label:hover {
  border-color: var(--primary);
  color: var(--primary);
  background: var(--primary-light);
}

.file-label i {
  font-size: 1.25rem;
}

.upload-actions {
  display: flex;
  gap: 0.75rem;
  margin-top: 0.5rem;
}

.btn-primary, .btn-secondary {
  flex: 1;
  padding: 0.75rem 1rem;
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  border: none;
}

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

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

.btn-secondary {
  background: var(--surface);
  color: var(--text-primary);
  border: 1px solid var(--border);
}

.btn-secondary:hover {
  background: var(--bg);
  border-color: var(--text-secondary);
}

/* Responsive */
@media (max-width: 640px) {
  .app-container {
    max-width: 100%;
    box-shadow: none;
  }
  
  .messages-wrapper {
    padding: 1rem;
  }
  
  .msg {
    max-width: 85%;
  }
  
  .upload-card {
    padding: 1.5rem;
  }
  
  .upload-section {
    padding: 0.75rem;
  }
}