function rainbow(radius) {
  var i, colors, bm;

  if (typeof radius == 'undefined') {
    radius = 18;
  }

  this.chkpt('rainbow');
  this.down(radius);
  // copy blocks.rainbow and add air at end (to compensate for strokewidth)
  colors = blocks.rainbow.slice(0);
  colors.push(blocks.air);
  for (i = 0; i < colors.length; i++) {
    bm = this.getBlockIdAndMeta(colors[i]);
    this.arc({
      blockType: bm[0],
      meta: bm[1],
      radius: radius - i,
      strokeWidth: 2,
      quadrants: {
        topright: true,
        topleft: true
      },
      orientation: 'vertical'
    })
      .right()
      .up();
  }
  return this.move('rainbow');
}
*********************************************************************
### Drone.rainbow() method

Creates a Rainbow.

#### Parameters
radius (optional - default:18) - The radius of the rainbow

#### Example

At the in-game prompt you can create a rainbow by looking at a block and typing:
```javascript
/js rainbow()
```

Alternatively you can create a new Drone object from a Player or Location object and call the rainbow() method.

```javascript    
var d = new Drone(player);
d.rainbow(30);
```

![rainbow example](img/rainbowex1.png)
*