I am a recent addition to itch, let alone this is the first jam I ever tried to participate in.
For me, it was the challenge. I managed to build an RPG (from scratch) in 128kb or less, so trying to do one in 10 days (in vanilla js with my own resource editor) was pushing my efforts to the limit (I have never made 8 music tracks in a single day, before), but I got it done.
https://kurogamedev.itch.io/nadines-fleet
15 stages, 10 music tracks, even I have trouble putting this game down once I get into playing it. It uses the same editor my rpg does and works out to around 130kb, complete (Though I made no effort to compress the code like I did with the RPG).