Every level starts with a number of red balls rotating around a starting ring, your starting point and where the balls return should you reset the level (with the [R] key). The goal is to get every red ball on the black ring, or at least as many as you need to progress to the next level. To do so, you'll need to click on a ball on the starting hoop, and then move your cursor accordingly to account for direction and intensity. Let go of the mouse button to release, and then it's all up to the simulated forces of nature. Until you start finding those items that allow you to click on and re-fire a ball, in midair. Then there's bumpers, and teleporters, and gravity changers, and even remorseless ball-popping spikes. See, now you feel bad for the red balls too.
Springen is not a challenge for the faint of brain; while there's a well-sized chunk of straightforward levels, there's a few dastardly rogues in there that ought to give you a run for your money. There's also a little bit of practice and skill involved, as the farther you have to lob those red globes, the less accurate you become and the more gravity becomes a fickle master. The balls are heavier than they look, and when you add a wealth of bumpers, gravity wells, and other gizmos between you and the ending hoop, some of the puzzles test your luck as opposed to your intellect.
Thankfully, the majority of the puzzles require crafty feats of ball-flinging, and you'll have to learn to use some of those obstacles to your advantage if you hope to make it through all 30 levels of phuzzling goodness. Maybe the red balls actually have a good deal, here in a physics puzzle; you're springing them out of the room for them, and they don't even need to touch a single screwdriver.