Every program is a puzzle.

They need to be solved. You can solve it in many fascinating ways. Some are simple, while some require many small solutions combined.

One thing I find fascinating is that you will never have a perfect solution. No matter how hard you try, there are always some things to tinker with. Make them more robust or make them even better. You feel like you are almost there but not there yet. So close, but yet so far at the same time.