Really interesting entry. It reminds me a little bit of 2048.

Like other comments say, the onboarding could be a little better (perhaps have a small number in the corner of each tile for its level? The green borders for upgradeable tiles are a nice touch).

The graphics are simple, but polished. The "age" meters look nice and the typeface matches the aesthetic of the game. A little extra sounds, effects, and feedback on various events (e.g. a tile dying) could push it to the next level.

My high score didn't seem to be written to, but I got as far as having two pink tiles on the board (and then promptly lost because I had neglected the rest of them... oops.

Good work for 72 hours!

After being confused initially and having asked you to update your page on how to play the game, you did update it, so thank you for that. I did understand how to play the game now, but must say for sure that it is rather complex and not something that everybody necessarily would understand in the first go. Also, when you mention the level of a tile, it would be really helpful to have a guide on which color represents each level, I kept forgetting what level the tile was as I was not able to determine it from its color. You did a good job on making a game that looks simple but has a complex idea to it. Well done, I hope you enjoyed making this game and please do take part in more game jams, it is a great source of learning and enjoyment.

Not 100% sure how to properly play this game tbh, it could use a tutorial video and a better explination really. I did like the idea you were going for and the simple art style works well. As for your saving and loading, that isn't that hard in game maker from what I recall. I made a game back in 2014/15 (GM 1.4) that used .ini files for level status saving. it was just a matter of opening, writing and saving the file. Not sure if GM 2 changed how that works though. I'd recommend looking into it as its a good feature for any game really. 

Still a good effort, well done!