Super D has a very classic problem: his friends have been locked away at the top of a huge tower, and the only way to rescue them is to climb it. Super D is a bright retro-style platformer from 2008, made by FreeWorldGroup, and it plays the way old platformers used to.
You move with the arrow keys, jump with the space bar, and use the number keys 1 to 9 for the items in the game. From the main menu you can open the Instructions page, which is worth reading before the first level. The tower goes up floor by floor, and every new floor means new enemies and awkward jumps.
Take it slowly on the tricky ones; running in blind is the quickest way to start over. For the most famous platformer of all, see Super Mario Bros, and for a precision test, Geometry Lite.