First of all, I refuse to call this a post-mortem, because post-partum is so much more appropriate, and no one died (this time :P).
After my failure in LD 35, I came back more determined than before to finish a game. And since my LD 34 entry didn’t have any music, I decided I wanted music in it this time.
What went right:
+ The music! It took some hours of screwing around with my recording device and with various Java audio interfaces, but I got my music to play in-game, on loop.
+ The gestalt — unlike last time, I managed to implement several different aspects of a game without getting distracted by one while working on another.
What went wrong (or could be better):
+ The art — it wasn’t so bad, I just didn’t enjoy making it. I’ll probably make a more abstract game next time, or else find an artist and enter the Jam.
+ The clicks — in a rush, I made it so that when you pick up an item, its upper-left corner, not its center, follows your mouse. This made it hard for players to put the items where they wanted, since they were probably aiming the center of the item where they wanted it to go.
+ The difficulty — without spoiling too much: one player noted that the game can be finished by trial and error, i.e. without actually solving the core puzzle. But, others enjoyed the more tangential challenges. Next time I’ll work on making every puzzle, or at least the important ones, harder to finish without actually solving them.
What (nearly) went ugly:
The very first two comments on my game, which I read before going to bed last night, both stated that they couldn’t run the game. I went to sleep thinking I had some huge problem that I’d need to solve, woke up stressed, and went immediately on LD.com to see if anyone had posted more details on the problem…only to find that other people had no problem, and that one of the two original commentors had realized the problem was on their end — their JVM needed to be updated — and fixed it. The other seemed to have unpacked the .jar, which was itself the runnable game, thinking that a different .jar would be inside.
I’ll still probably write the next game in Java 7 and put it in a .zip with instructions, though, just to make it silliness-proof 

Lione’s Letter
Lione’s Letter can be played here.