I take it that "First Dungeon" is more of a literal "this is my First game, set inside a Dungeon!" then?
While the visuals are alright, there's just a lack of polish in the game overall. A lack of sprites to account for terrain geometry causes a lot of ugly appearances in the levels, like in the screenshots provided.
The controls don't feel nice at all. Among other issues with movement if you try to jump a moment you go off a ledge, you end up plummeting you to your death. Might be wise to give this a check out: https://gmtk.itch.io/platformer-toolkit
Have only played up to half of the third level, quitted because not only did I die out of nowhere without being near the blobby enemy, but I feel like the ending would've been lackluster as the title screen.