|
## CSS Selectors
### Basic Selectors
| Command | Description |
|---------|-------------|
| `element` | `p { }` — all elements |
| `.class` | `.card { }` — class selector |
| `#id` | `#main { }` — id selector |
| `*` | Universal selector (all elements) |
### Combinators
| Command | Description |
|---------|-------------|
| `A B` | Descendant (B inside A) |
| `A > B` | Direct child only |
| `A + B` | Adjacent sibling (B right after A) |
| `A ~ B` | General sibling (B after A) |
### Pseudo-classes
| Command | Description |
|---------|-------------|
| `:hover` | Mouse over element |
| `:focus` | Element has focus |
| `:first-child` | First child of parent |
| `:nth-child(n)` | nth child (2n = even, odd) |
## Box Model
```
.box {
margin: 10px; /* outside */
border: 1px solid #333; /* edge */
padding: 15px; /* inside */
width: 200px;
box-sizing: border-box; /* include pad+border */
}
```
### Shorthand
| Command | Description |
|---------|-------------|
| `margin: 10px` | All sides |
| `margin: 10px 20px` | Top/bottom \| left/right |
| `margin: 10px 20px 15px` | Top \| left/right \| bottom |
| `margin: 10px 20px 15px 5px` | Top \| right \| bottom \| left |
## Flexbox
### Container
```
.flex-container {
display: flex;
flex-direction: row; /* row | column */
justify-content: center; /* main axis */
align-items: center; /* cross axis */
gap: 10px;
flex-wrap: wrap;
}
```
### Item Properties
| Command | Description |
|---------|-------------|
| `flex: 1` | Grow to fill available space |
| `flex-grow: 2` | Grow ratio relative to siblings |
| `flex-shrink: 0` | Don't shrink below basis |
| `flex-basis: 200px` | Initial size before grow/shrink |
| `align-self: flex-end` | Override container alignment |
| `order: -1` | Visual order (default 0) |
## Grid
### Container
```
.grid {
display: grid;
grid-template-columns: 1fr 2fr 1fr;
grid-template-rows: auto;
gap: 10px;
}
```
### Item Placement
```
.item {
grid-column: 1 / 3; /* span col 1-2 */
grid-row: 1 / 2;
}
/* shorthand: repeat, minmax */
grid-template-columns: repeat(3, 1fr);
grid-template-columns:
repeat(auto-fit, minmax(200px, 1fr));
```
## Positioning
| Command | Description |
|---------|-------------|
| `static` | Default flow (no offset properties) |
| `relative` | Offset from normal position |
| `absolute` | Offset from nearest positioned ancestor |
| `fixed` | Offset from viewport (stays on scroll) |
| `sticky` | Relative until scroll threshold, then fixed |
### Example
```
.parent { position: relative; }
.child {
position: absolute;
top: 0; right: 0; /* top-right corner */
}
```
## Media Queries
```
/* Mobile-first: base styles for small screens */
.container { padding: 10px; }
@media (min-width: 768px) {
.container { max-width: 720px; }
}
@media (min-width: 1024px) {
.container { max-width: 960px; }
}
```
### Common Breakpoints
| Command | Description |
|---------|-------------|
| `480px` | Small phones |
| `768px` | Tablets |
| `1024px` | Small desktops / landscape tablets |
| `1280px` | Desktops |
```
### Lists
```