Use the arrow keys to move the ball. You can edit the game area by clicking on blocks or on the overhead map in the upper-right corner.
When you click on a block or tile on the map, this will select the whole vertical stack of blocks, you can then insert and delete blocks.
You can delete blocks directly by shift-clicking a block in the game area, or clicking a little X button on the right of a block in the stack.
You can add blocks by control-clicking on the game area or by using the little arrows at the left of the selected stack.
Holding the Alt or Option key will enable an experimental (but slow) light spot effect around the ball.

Requires the Shockwave plug-in version 10.x