The hitboxes may provide some stupid deaths, but that's what makes it challenging and fun. Tip: it helps to take your time on the levels that let you do so, as taking it slow can help prevent deaths that would otherwise happen if you rush through the levels
Don't use the bird thing to fly up to the top of the ledge in Level 2, there's nothing up there, and flying up to the top of the screen will kill Tri-achnid