A computer game on a computer theme. On screen is a Basic program with some of its letters and numbers missing. They've been stolen by little bugs who hid them in boxes at the corners of the screen.
You control a mouse whose job is to put them back into position. This is easier than it sounds because the screen shows you where each missing character should be, and even tells you which box to collect it from. The problem is purely to replace the letters faster the bugs can steal them.
This is easy at first, but gets progressively harder. You may have to resort to destroying the bugs with a spray you can squirt at them - although it's hard to see what this achieves since they're immediately replaced.