Alright, i have 3 mystery games for you. I played them all around 2000, give or take a couple of years. The first is a 3d jet fighter sort of game, but it was heavily blocky, like legos. at the beginning of each level, you were given a certain amount of points to spend on upgrades such as extra lives or stronger firepower. your missions were to destroy buildings and enemy ships, which exploded upon destruction. I also recall that you could fly nearly into space if you flew up for long enough.
the second was a sidescroller game, where you are a guy who walks through a level shooting enemies with grapes and fruit. there is one level i specifically remember where you get on a bike and race a whole bunch of other guys to the finish by repeatedly pressing a key.
The final game is a puzzle game, where you play as a spinning diamond on a flat (floating?) environment (no walls, you fall off into nothingness). it is very physics based, where speed and direction play a large part. in the first level, you can access a hidden area by moving very fast towards an angled part that acts as a ramp. if you move too slow, you dont make the distance. the floor is i think checkered and there are various enemies that i cant remember. it had a similar look and feel to the miniclip.com game gyroball.
with screenshots, i could maybe identify the games by the picture.
EDIT
These were all computer games, but am not sure of the os. might be an old macintosh computer but again, not totally sure.