botserver/docs/src/chapter-05-gbtheme/css.md

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# CSS Customization
The **gbtheme** CSS files define the visual style of the bot UI. They are split into three layers to make them easy to extend.
## Files
| File | Role |
|------|------|
| `main.css` | Core layout, typography, and global variables. |
| `components.css` | Styles for reusable UI components (buttons, cards, modals). |
| `responsive.css` | Media queries for mobile, tablet, and desktop breakpoints. |
## CSS Variables (in `main.css`)
```css
:root {
--primary-color: #2563eb;
--secondary-color: #64748b;
--background-color: #ffffff;
--text-color: #1e293b;
--border-radius: 8px;
--spacing-unit: 8px;
}
```
Changing a variable updates the entire theme without editing individual rules.
## Extending the Theme
1. **Add a new variable** Append to `:root` and reference it in any selector.
2. **Override a component** Duplicate the selector in `components.css` after the original definition; the later rule wins.
3. **Create a dark mode** Add a `@media (prefers-color-scheme: dark)` block that redefines the variables.
```css
@media (prefers-color-scheme: dark) {
:root {
--primary-color: #3b82f6;
--background-color: #111827;
--text-color: #f9fafb;
}
}
```
## Best Practices
* Keep the file size small avoid large image data URIs; store images in `assets/`.
* Use `rem` units for font sizes; they scale with the root `font-size`.
* Limit the depth of nesting; flat selectors improve performance.
All CSS files are loaded in `index.html` in the order: `main.css`, `components.css`, `responsive.css`.
## Component Styling Guide
### Message Bubbles
Customize chat message appearance:
```css
/* User messages */
.message-user {
background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
color: white;
padding: 12px 16px;
border-radius: 18px 18px 4px 18px;
max-width: 70%;
margin-left: auto;
}
/* Bot messages */
.message-bot {
background: #f7fafc;
color: #2d3748;
padding: 12px 16px;
border-radius: 18px 18px 18px 4px;
max-width: 70%;
border: 1px solid #e2e8f0;
}
/* Typing indicator */
.typing-indicator {
display: inline-flex;
padding: 16px;
background: #edf2f7;
border-radius: 18px;
}
.typing-indicator span {
height: 8px;
width: 8px;
background: #718096;
border-radius: 50%;
margin: 0 2px;
animation: typing 1.4s infinite;
}
```
### Input Field
Style the message input area:
```css
.input-container {
padding: 16px;
background: white;
border-top: 1px solid #e2e8f0;
}
.input-wrapper {
display: flex;
align-items: center;
background: #f7fafc;
border: 2px solid #e2e8f0;
border-radius: 24px;
padding: 8px 16px;
transition: all 0.2s;
}
.input-wrapper:focus-within {
border-color: var(--primary-color);
background: white;
box-shadow: 0 0 0 3px rgba(66, 153, 225, 0.1);
}
.message-input {
flex: 1;
border: none;
background: transparent;
outline: none;
font-size: 16px;
}
.send-button {
background: var(--primary-color);
color: white;
border: none;
border-radius: 50%;
width: 36px;
height: 36px;
display: flex;
align-items: center;
justify-content: center;
cursor: pointer;
transition: transform 0.2s;
}
.send-button:hover {
transform: scale(1.1);
}
.send-button:active {
transform: scale(0.95);
}
```
### Buttons
Consistent button styling:
```css
/* Primary button */
.btn-primary {
background: var(--primary-color);
color: white;
border: none;
padding: 10px 20px;
border-radius: 8px;
font-weight: 500;
cursor: pointer;
transition: all 0.2s;
}
.btn-primary:hover {
filter: brightness(110%);
box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}
/* Secondary button */
.btn-secondary {
background: transparent;
color: var(--primary-color);
border: 2px solid var(--primary-color);
padding: 8px 18px;
border-radius: 8px;
font-weight: 500;
cursor: pointer;
transition: all 0.2s;
}
.btn-secondary:hover {
background: var(--primary-color);
color: white;
}
/* Icon button */
.btn-icon {
background: transparent;
border: none;
width: 40px;
height: 40px;
border-radius: 50%;
display: flex;
align-items: center;
justify-content: center;
cursor: pointer;
transition: background 0.2s;
}
.btn-icon:hover {
background: rgba(0, 0, 0, 0.05);
}
```
## Animation Library
### Entrance Animations
```css
@keyframes slideInUp {
from {
transform: translateY(20px);
opacity: 0;
}
to {
transform: translateY(0);
opacity: 1;
}
}
@keyframes fadeIn {
from { opacity: 0; }
to { opacity: 1; }
}
@keyframes scaleIn {
from {
transform: scale(0.95);
opacity: 0;
}
to {
transform: scale(1);
opacity: 1;
}
}
/* Apply animations */
.message {
animation: slideInUp 0.3s ease-out;
}
.modal {
animation: scaleIn 0.2s ease-out;
}
```
### Loading States
```css
/* Spinner */
.spinner {
width: 40px;
height: 40px;
border: 3px solid #e2e8f0;
border-top-color: var(--primary-color);
border-radius: 50%;
animation: spin 0.8s linear infinite;
}
@keyframes spin {
to { transform: rotate(360deg); }
}
/* Skeleton loader */
.skeleton {
background: linear-gradient(90deg, #f0f0f0 25%, #e0e0e0 50%, #f0f0f0 75%);
background-size: 200% 100%;
animation: loading 1.5s infinite;
}
@keyframes loading {
0% { background-position: 200% 0; }
100% { background-position: -200% 0; }
}
```
## Responsive Design Patterns
### Mobile-First Approach
```css
/* Base mobile styles */
.container {
padding: 16px;
width: 100%;
}
/* Tablet and up */
@media (min-width: 768px) {
.container {
padding: 24px;
max-width: 768px;
margin: 0 auto;
}
}
/* Desktop */
@media (min-width: 1024px) {
.container {
padding: 32px;
max-width: 1024px;
}
}
/* Wide screens */
@media (min-width: 1440px) {
.container {
max-width: 1280px;
}
}
```
### Touch-Friendly Styles
```css
/* Increase touch targets on mobile */
@media (pointer: coarse) {
button, a, input, select {
min-height: 44px;
min-width: 44px;
}
.btn-primary, .btn-secondary {
padding: 12px 24px;
font-size: 16px;
}
}
/* Disable hover effects on touch devices */
@media (hover: none) {
.btn-primary:hover {
filter: none;
box-shadow: none;
}
}
```
## Theme Variants
### Dark Mode
```css
@media (prefers-color-scheme: dark) {
:root {
--primary-color: #60a5fa;
--secondary-color: #94a3b8;
--background-color: #0f172a;
--text-color: #f1f5f9;
--border-color: #334155;
}
.message-bot {
background: #1e293b;
color: #f1f5f9;
border-color: #334155;
}
.input-wrapper {
background: #1e293b;
border-color: #334155;
}
}
```
### High Contrast
```css
@media (prefers-contrast: high) {
:root {
--primary-color: #0066cc;
--text-color: #000000;
--background-color: #ffffff;
}
* {
border-width: 2px !important;
}
button:focus, input:focus {
outline: 3px solid #000000 !important;
outline-offset: 2px !important;
}
}
```
## Performance Tips
1. **Use CSS Variables**: Change themes by updating variables, not entire stylesheets
2. **Minimize Specificity**: Keep selectors simple for faster parsing
3. **Avoid Deep Nesting**: Maximum 3 levels deep
4. **Use Transform/Opacity**: For animations instead of layout properties
5. **Lazy Load Non-Critical CSS**: Load theme variations on demand
## Browser Compatibility
```css
/* Provide fallbacks for older browsers */
.gradient-bg {
background: #3b82f6; /* Fallback */
background: linear-gradient(135deg, #3b82f6 0%, #8b5cf6 100%);
}
/* Use @supports for progressive enhancement */
@supports (backdrop-filter: blur(10px)) {
.modal-backdrop {
backdrop-filter: blur(10px);
}
}
```
## See Also
- [Theme Structure](./structure.md) - File organization
- [Chapter 4: User Interface](../chapter-04-gbui/README.md) - Applying themes to templates
- [Chapter 6: BASIC](../chapter-06-gbdialog/README.md) - Dynamic theme switching
## Next Step
Return to [Chapter 5 Overview](./README.md) or continue to [Chapter 6: BASIC Dialogs](../chapter-06-gbdialog/README.md).