There's definitely a difference between the result, and the way something was built or put together. I'd congratulate them on the result and tell them what they

There's definitely a difference between the result, and the way something was built or put together. I'd congratulate them on the result and tell them what they did right, code wise. I'd also perhaps point out some (major) areas where they could've done better, so they could take that knowledge and use it in the next app or game they decide to build.