You can pass the Bridge Troll, the Restless Spirit, and the Lava Wyrm. To skip the troll, you have to climb up the slanted wall. Normally you'll just slide off, but if you attack you'll stop sliding and can jump before you start sliding again. The most practical way to do this is to attack and jump at about the same time. I skip the spirit in the same way on the top right slant but it's a bit different. If you just jump up and to the right as far as you can, the game basically softlocks. You don't advance screens and you are nowhere to be seen. So what I do is jumnp once to the right and then time a jump to the left offscreen. This makes you leave the room from the top and I guess the game doesn't care which way you leave the screen as long as you leave it. I tried a couple different ways to skip the wyrm, including trying to damage-boost across the gap by praying the wyrm moved to the right with me, but it didn't work. Then I realized you can jump off the lava as soon as you hit it. So I just jump off the spawn platform and then off the lave before the wyrm even appears
3 other cool things I found
In the slime boss fight, it's possible to beat the slime without the slime rising. you can hit it for 36 damage, then defeat it in one appearance while you're on 1hp.
In the room before the reflection boss when you first see your reflection, you can inch yourself towards the right end of the screen and fall to the bottom, switching spots with the reflection. You can no longer see yourself, but just move to the right and you'll go to the bossfight.
In the room before the lava wyrm boss, you can finagle your way into the walls by jumping into the slants on the left and right parts of the walls
I love your game! Thanks for making it :)