Extremely impressive game! It's a very full featured metroidvania considering the time and (jam-imposed) technical limitations. A map and inventory screen, multiple bosses, a bunch of hidden upgrades and collectables... the works! Having no jump button is an interesting idea and leads to needing to think about how to navigate in a very different way.
If I had to make one criticism, it's the fact that it can be ambiguous whether the edge of the screen is a room transition, wall, or pit. It would also be nice if there was a button or something to quickly check your health.