One of the rules is that the resolution of the game must be "16:10 (1600:1000 px) or 16:9 (1600:900 px)".

However, I'm a bit confused and would like a bit more information. Are those the only resolutions to use, or could I also use something like 1920x1080, which is still 16:9?

Hi, i've made this same question on Hisarjam 2 on discord, this is the answer.

Yes, you can use 1920x1080px, b\ut we still encourage you to make it 16:10 (1600:1000 px) or 16:9 (1600:900 px).