Thanks for all the kind words! Watching this gameplay gave me a lot of information. First off that it looks like it took some time before you realized how new grains were planted (since you drove around with the harvester down a lot in the beginning, even if you had nothing to harvest) Luckily it seems you got the hang of it around the 2 minute mark.
Glad you like the "pling" upgrade sound, made it in like 2 minutes when there was 30 minutes to the deadline and I rushed to get the upgrade system in.
It was certainly a trial and error math process of getting the tractor to always align with the ground + speed getting influenced by the slope. (I'm not using the built in rigid body system for this, so I'm glad you notice it!)
I'm sorry about the performance issues triggering so early. With my computer it can still run it just fine in web even with 1000+ grains out. (You had around 800). Thankfully each grain is only 12 vertices!
I'll think about expanding it. First on the list would be to make the song longer and make it possible to pick different upgrades. I also wanna incorporate the mill in gameplay somehow. (making flour?)
Thanks again for playing!