Jumping Line is a really great horizontal scrolling game. I guess you could also call it a puzzle, because it is very challenging. But it is also very fun to play. In this game, you control a single line and your objective is to jump from platform to platform without falling. You control the line with your mouse. If you move the mouse to the far right, the line will bounce more to the right. If you move the mouse to the left, the line will either move back or jump in place if you place it in the middle. Every few obstacles you will find black platforms that serve as checkpoints. When you land in one of these, multiple lines will shoot up from it and then they will disappear. This means you have reached a checkpoint. When you fall, you start from the last checkpoint you hit. I don't think you ever lose in this game. I fell several times and I always restarted from the last checkpoint.
In short, Jumping Line is a great game to have installed on your Mac. It costs only $0.99 and it can be played for quite a while. Every once in a while I stumble upon developers who do great things with simple things, like a line in this case, and I have to congratulate them. They created an interesting game based on one of the simplest things I can think of.