This is probably the most interesting section. Using constraints is almost compulsary to design a good quality level, so understanding how they work is crucial. The editor allows to combine all constraints on the same object, but some will overpower others and make them useless, so it's good to find out which ones can be combined and which ones shouldn't. (Combining incompatible constraints may result in unstable objects, and even making them fly off screen.) You can even use the same constraint with different parameters multiple times on the same object. It's impossible to describe all combinations, so experimenting is the key here. Please keep in mind that I am not part of Silicon Studio (the creater of Pixel Rain) and that I had to figure these out all by myself too. Secondly, my primary language isn't English but I'll do my best trying to explain them. Click on a red button to see a detailed explanation of the constraint.