svg-animations

这段内容是审核时保存的快照。外部来源才是完整且最新的版本。

---
name: svg-animations
description: Create beautiful, performant SVG animations and illustrations. Use this skill when the user asks to create SVG graphics, icons, illustrations, animated logos, path animations, morphing shapes, loading spinners, or any animated SVG content. Covers SMIL animations, CSS-driven SVG animation, path drawing effects, shape morphing, motion paths, gradients, masks, and filters.
---

This skill guides creation of handcrafted SVG animations — from simple animated icons to complex multi-stage path animations. SVGs are a markup language for images; every element is a DOM node you can style, animate, and script.

## SVG Fundamentals

### Coordinate System
SVGs use a coordinate system defined by `viewBox="minX minY width height"`. The viewBox is your canvas — all coordinates are relative to it, making SVGs resolution-independent.

```svg
<svg viewBox="0 0 200 200" xmlns="http://www.w3.org/2000/svg">
  <!-- 200x200 unit canvas, scales to any size -->
</svg>
```

### Shape Primitives

```svg
<rect x="10" y="10" width="80" height="40" rx="4" fill="#1a1a1a" />
<circle cx="50" cy="50" r="30" fill="#e63946" />
<ellipse cx="50" cy="50" rx="40" ry="20" fill="#457b9d" />
<line x1="10" y1="10" x2="90" y2="90" stroke="#2a9d8f" stroke-width="2" />
<polygon points="50,5 95,90 5,90" fill="#e9c46a" />
<polyline points="10,80 40,20 70,60 100,10" fill="none" stroke="#264653" stroke-width="2" />
```

### The `<path>` Element — The Power Tool

The `d` attribute defines a path using commands. Uppercase = absolute, lowercase = relative.

| Command | Purpose | Syntax |
|---------|---------|--------|
| M/m | Move to | `M x y` |
| L/l | Line to | `L x y` |
| H/h | Horizontal line | `H x` |
| V/v | Vertical line | `V y` |
| C/c | Cubic bézier | `C x1 y1, x2 y2, x y` |
| S/s | Smooth cubic bézier | `S x2 y2, x y` |
| Q/q | Quadratic bézier | `Q x1 y1, x y` |
| T/t | Smooth quadratic | `T x y` |
| A/a | Elliptical arc | `A rx ry rotation large-arc sweep x y` |
| Z/z | Close path | `Z` |

**Cubic Bézier** (`C`): Two control points define the curve. The first control point sets the departure angle, the second sets the arrival angle.

```svg
<path d="M 10 80 C 40 10, 65 10, 95 80" stroke="#000" fill="none" stroke-width="2" />
```

**Smooth Cubic** (`S`): Reflects the previous control point automatically — perfect for chaining fluid S-curves.

```svg
<path d="M 10 80 C 40 10, 65 10, 95 80 S 150 150, 180 80" stroke="#000" fill="none" />
```

**Arc** (`A`): `rx ry x-rotation large-arc-flag sweep-flag x y`
- `large-arc-flag`: 0 = small arc, 1 = large arc (>180°)
- `sweep-flag`: 0 = counterclockwise, 1 = clockwise

```svg
<!-- Heart shape using arcs and quadratic curves -->
<path d="M 10,30 A 20,20 0,0,1 50,30 A 20,20 0,0,1 90,30 Q 90,60 50,90 Q 10,60 10,30 Z"
      fill="#e63946" />
```

### Grouping and Transforms

```svg
<g transform="translate(50, 50) rotate(45)" opacity="0.8">
  <rect x="-20" y="-20" width="40" height="40" fill="#264653" />
</g>
```

Use `<g>` to group elements for collective transforms, styling, and animation targets.

### Gradients, Masks, and Filters

```svg
<defs>
  <!-- Linear gradient -->
  <linearGradient id="grad" x1="0%" y1="0%" x2="100%" y2="100%">
    <stop offset="0%" stop-color="#e63946" />
    <stop offset="100%" stop-color="#457b9d" />
  </linearGradient>

  <!-- Radial gradient -->
  <radialGradient id="glow" cx="50%" cy="50%" r="50%">
    <stop offset="0%" stop-color="#fff" stop-opacity="0.8" />
    <stop offset="100%" stop-color="#fff" stop-opacity="0" />
  </radialGradient>

  <!-- Mask -->
  <mask id="reveal">
    <rect width="100%" height="100%" fill="black" />
    <circle cx="100" cy="100" r="50" fill="white" />
  </mask>

  <!-- Blur filter -->
  <filter id="blur">
    <feGaussianBlur in="SourceGraphic" stdDeviation="3" />
  </filter>
</defs>

<rect width="200" height="200" fill="url(#grad)" />
<rect width="200" height="200" fill="url(#grad)" mask="url(#reveal)" />
<circle cx="50" cy="50" r="2