This is seriously impressive to be built from scratch. The engine really feels full-featured and seems to have everything you'd need, and the game itself is fun and has a really nice feel to it. The main issues I had were bugs and balance. I did miss the fact that you can recruit multiple party members the first couple plays, but even after figuring that out it still seems on the difficult side. I went out with a full party and managed to defeat the tiger, but all except one of my guys were wiped out by the tiger's one hit kill jump attack. Trying to get back with one guy was a struggle, as I was getting two-spider encounters every couple steps, so I didn't end up making it.
There did seem to be some bugs, or maybe I'm not understanding the controls. Sometimes when I load the game, the keyboard doesn't work, others the cursor keys work but the mouse doesn't click buttons (sometimes I can see the button change color on click, but it does nothing). I was never able to hear any music at all. I also got stuck on the inventory screen twice, as I couldn't find any way to exit it. Escape just gives the option to quit or return to the game. Overall though, pretty good for what I'd expect on day 10 of developing a brand new RPG engine!
I also really like the visuals (I've used this tileset in the past and know how much work it takes to make it really look good), especially given the palette. The animations were really fluid and everything felt alive. I hope you're able to keep working on the engine code and use it again in your next jam!