Making a game in 20 lines of code made it very clear to me how much effort there is in building the mechanics of the game compared to how much effort goes into making the player feel comfortable in your game.  8 lines for the mechanics to work, less if I have an if and an instruction on the same line, and the other 12 lines to provide feedback. A 40/60 split.

I'd say the same about designing the levels. Many of the levels were there just to clue players in on how things worked and very few were actually meant to be a challenge.

We all know feedback is important for the player, but this project made me see exactly how important it is compared to the part that we tend to think is the important one, the mechanics that make the game different from everything else.  

So I guess from now I'll be more comfortable privileging feedback over new features. It's like a restaurant, people come for the food but they stay because there's a whole building built around that dish you're serving.

This was my first game and my first game jam so I learned a lot. Especially about the last mile kind of stuff I have never thought about like setting up the game page, building for multiple platforms, troubleshooting build issues, getting screenshots, making a trailer video and so on. I probably should have thought more about that earlier on.

I will say I had to spend a lot of time getting things to feel right. What I ended up submitting was not what I had in mind when I started at all. I had to simplify the gameplay because I spent a lot of time tuning the camera, getting the shot to feel right, and trying to find 20 ways to meet to the 20 theme. There just wasn't enough time left at the end to get the gameplay working the way I wanted. I thought my scope was small enough in the beginning, but I was wrong. I had to submit a day early due to personal obligations, but I don't think the extra day would have been enough anyway. I was just too ambitious and inexperienced to get to where I wanted to be.

I also learned how frustrating, fun, nerve wracking, and ultimately satisfying it is take part in a game jam.

I also made a game in 20 lines of code! And while I already knew about this feature, I learned a new way to use it.

conditional operators (GameMaker Manual Link)

variable = (condition ? expression1 : expression2);

While above is what I already knew, below is what I learnt from reading the manual during the jam.

function( <parameter_1>, <condition ? parameter_2_a : parameter_2_b> );

Using conditional operators in place of function parameters saved a LOT of lines of code for my game! It allowed me to toggle between a music tack when the game is running and an ambient track for when the player dies. It also allowed me to change the direction and object rotates after a specific amount of time. Fun stuff!

I've never made a rhythm game before, and learned that a game set to run at a speed of 60 can only get so precise in terms of timing beats to a song. This limited my accuracy to the tenth decimal place of a second instead of hundreds or thousands as would be preferred.

Something I've never considered!

I learnt to put off all of the new ideas I come up with making games. Usually they are enough to derail a project into digital dirt, but this time, as I was doing my first jam, I managed to get on with my goal. I didn't manage to get as much done as I wanted anyway, so it's a good thing I didn't start adding new features! I also learned that I can finish a game (even if it's a mess :D) and post it here really easily. 

Feel free to try it https://firath.itch.io/nostalgic

Each time I start a game project, for game jam or outside of it, I learn that it's best to cut off most features that you get an idea for. Also, it's really not the best idea for game jams to start making a game thinking you'll make a huge RPG. XD Trying to keep things simple and fun is a skill on its own. I've yet to master that. 
Anyway, what I learned during this jam was how to make a crude lighting/shadow system with just a couple lines of code. Very simplistic and works well enough for me.

You may see the lighting system in action here: https://itch.io/jam/gamemaker-20/rate/520409

i've never used gms2 before so i've learned about it's sandboxing feature that almost screwed my game xD

I don't really feel like I learned anything, but it's probably because I worked super intensely during one day and then dropped the project... no time for introspection / retrospection. Most of the code I wrote without access to GM, then I copypasted the script into objects / scripts once I got home, so there was no time to tweak and polish. It let me achieve a lot of stuff in a short time, so maybe I'm test playing too much and focusing too hard on game feel when I can just test every line of code before proceeding?

I implemented exactly 2 changes to my orginal ideas:

• Animals originally had a value based on the number of letters in their name. I had to cancel this because some puzzles needed 1s or 2s and I couldn't come up with any animals with names 1 or 2 letters long.
• I hadn't originally planned the "unknown" operators, but I realized hiding information from the player and forcing them to experiment a bit essentially would fit pretty well with how they'd need to tackle some of the more obscure operators (multiplication and division doesn't bind tighter than plus/minus in 20w0 Keeper, the square-and-add / cube-and-add / backwards square root operators aren't super self-explanatory) so it would be a natural progression in difficulty. Since I was starting to run out of ways to make the maths harder around lv.10, I decided to make 10 more levels with more and more unknown operators.

I already knew in beforehand that you get the best ideas when you test play a game, seeing what of your original ideas works and what doesn't, but it's always good with a refresher.

My submission is the first game I've done to the point of being a playable thing, I've messed around with some ideas in GameMaker before but never finished anything. This is also the first jam I've taken part in. I think what's struck me most about it is being able to say "that'll do" to myself.

My submission isn't exactly what I had in mind when I started, there's a few things that I'd have liked to have implemented that I couldn't get working in a way I was happy with, I was largely learning as I went. The time constraint forced me to not get bogged down with what I wanted the game to do and instead focus on getting the basics done and working around my own limitations as a coder.  I wouldn't exactly say what I've submitted is 'finished', and I'll probably go back to it at some point and try adding some things in, but it's a playable game and I'm happy with how it's turned out :)

Also, I learned that drawing 20 by 20 pixel scenes is frustrating but quite satisfying. 

That I need an artist (I have one he was just busy)

I mean my pixel art sucked ass

I like writing a ton (and not just for the game, mind you) so rather than spamming the thread with a wall of text, here's a postmortem about our entry into the jam (The Best Birthday)!