I'm not quite sure how to write a postmortem myself, but I think I'll share it here what I've learned from this jam.
1. Doing the animations without references, can take an immense amount of time. Was reluctant to use references to stay "original/creative", but really, in the end it's basic movement, one way or another it's going to look similar.
- Cons? Takes a tremendous amount of time, and it may not look good, then making it public for feedback, you fix it accordingly and it looks good,, but it also looks like the thousands of references you'll find online.
- Pros? You sort of end up getting quite comfortable with the animation tools that you're using (my case - Godot, setting keyframes etc), You'll also be able to produce animations that are in your head more easily after this exercise. (So I don't regret the time spent)
But for a game jam, you probably don't want to be stuck on these for a long time. It took me around 3 days to get the basics done, running, jumping, sliding. Then an extra 2 days for Falling, Landing, Crouching.. It did pay off in the end though.
2. Sound Effects takes a long time (if you're not doing it yourself), I've never done it myself, so I can only imagine it being faster. I procrastinated sounds till the last day. I thought I could just easily download some free sfx and put into the game. While that's true.. what I didn't know, is that is hard to find the "suitable" sound for your game. Overall took me about 6 hours to get half of the sfx that I needed for my game.
And also, learn a bit about your audio editing software, you'll find out that is quite easy to do the essentials...
3. Simple > Complicated.
I've implemented a "new / revolutionary / patent-pending " mechanic that sounded sophisticated at first, it was so new, that it just confused all the players who tried it. Not only that, it was hard to code it, hard to explain and understand how it works, and not very well received.
Ended up replacing with something extremely simple, something that every was familiar instead. Result? Easier to code, and comments about how weird / confusing it was, were just completely gone.
4. Experiment, experiment and experiment...
You'll never know, sometimes your greatest ideas just come from experiments, specially if you're failing to do/create something that you want, but doesn't quite have the idea formulated.
This is for now ;P