cp's spiral of Conway's game of life

Frame (ish):

Rather than all the cells in the grid being updated at once for each frame, a cursor winds outwards from the centre, updating each cell as it goes.

But that isn't all! When all of a cell's neighbours are on the same frame, it gets to do an extra update.

The end result is the same as the normal game, but the way it gets there is different.

Click on cells to change their state, but beware that unless the cursor is at the bottom-right of the grid, adjacent cells might be on different frames.

Refresh the page to reset the game, because I have done my d3.js badly.