Just caught up on xkcd, particularly liked this one:
(Wouldn't a Sisyphean version be worse?)
It triggered a thought - how about a version of tetris with
non-regular blocks, which would reach some kind of critical mass when
enough were placed close together? Each time critical mass was
reached, it could explode in the box, with larger explosions leaving
less stuff at the bottom. Maybe some radioactive blocks and some
absorber blocks, with all the physics being simulated for critical
Later levels could have less random combinations of absorber and
emitter, or more concave shapes which are harder to fit together, etc.
graphics programming, polygon collision-detection, physics simulation
(both for the critical mass stuff and the resulting kinetics) and user
interaction for the controls.