From the 90%-scoring review:
The elements introduced as you progress through the game are all meant to get you thinking, and should apply to anyone who used to play with string and rubber bands in their childhood! There are sliding tethers to carry the candy around. If the candy is hooked onto two ropes at once, you can slide them apart, until the rope turns red, which means the rope under tension. Cutting the rope releases all that energy and you the candy is fired like a shot. In the later levels you take to space and get to play with an artificial gravity field. In addition to these devices, there are hazards like electric arcs, and spiders that crawl down the rope wanting to steal the candy.
ZeptoLab deserve credit for keeping the gameplay of Cut the Rope fresh by varying the gameplay. It frequently switches between levels that take a lot of thought and others that take fast reactions. Even those types of levels are punctuated by fun levels that are there just for the sake of performing a cool trick.