If you are planning to update a game you made with an earlier version of the engine, you may be in for a surprise. I decided to do just that. What I thought would take a few hours--better models, better animation, better terrain, etc.--ended up taking a couple weeks.

The modeling and terrain went easily. But the code, which used a lot of A5 template stuff, was the nightmare. Everything I improved produced a bug somewhere else.

In the end, it might have been less trouble to remake the game from scratch.