So the original reason I bought Jumping Line was because it was only a dollar on Desura!
Jumping Line is one of the most basic platformers I've played, controlled completely by moving the mouse left to right. Moving the mouse to the left makes the line go left and moving the mouse right makes the line go right. Despite these simple controls this game is fun and can be challenging at times.
I'd classify this game as a casual game, whenever you get to a checkpoint it saves, so you can exit at pretty much any time, and unlike some platformers it doesn't feel intense in the slightest.
Mostly what makes this game different is the simple controls and the level design, it seems to be one really really long level with various different mechanics involved. It starts off very simple, make it across the gaps, after that they start throwing stuff at you, standard platforms moving back and forth at first, rotating blocks you have to jump across, changing it so you are jumping off the ceiling instead of the floor, some parts you have to gather a set amount of (I can't remember exactly what it is...) stars (I think) to carry on. Though for gathering the stars there is no real death penalty, if you die, you restart at your last checkpoint, everything you gathered is still counted as gathered, so it's a very casual game.
Simple, casual, only a buck, what's not to love about Jumping Line?