(This code is probably going away, but…) Stylistically, I think these comments would look slightly better on the same line as the code:

```js
touchtime = null; // prevent spurious dbltap
started(); // recompute touch locations
```

Also, I tend to use lowercase with no terminating period for end-of-line comments, since these are usually sentence fragments or words so as to limit their length and fit them on the same line.