The Maze could be played in TPOTS/CC as well. It was easy to convert it with PRPTool. All that is needed is a change of version number.
If you really want to talk about early puzzles you may as well mention the Walker game. Back then there were no released age building tools so this was all done in Python by modifying existing UU ages. While there were some in-game visuals it was mostly text based, using dynamic texts within existing objects and books. The tasks to be performed were very real though (and not unlike the easter egg mission from which I stole the concept). To make it all work several existing clickables were given additional functions.
The Walker game was intended as a userKI extension which could be enabled/disabled from the server side. This btw was the way the userKI was going: All of its features would be off by default and then shard admins could allow them on an individual basis.
Unfortunately the userKI was abandoned when people started taking their own userKI "enhancements" to our shards, which in the process messed up our vaults. And with the userKI the Walker game died as well. So it never went public, but we had quite a few testers at the time whose reactions were unanimously positive. You know who you are.
As a point of interest, some of you may have studied the UU game files and noticed the Walker shirt in there. That shirt was to be the reward for completing the Walker game and its inclusion in UU was a clerical error on my part.
I was working on multiple clothing additions for UU and forgot to remove it from my final submission. Not that it really mattered since it was a hidden reward item with no trigger implemented for distribution.