In this cave level, you need to use a Press (You need to Spinjump off of it, since idk what the code is for enemies being ridable), that never rise, much like the Press from Cave Story. And, I took advantage of the extra space of the Underground tileset to add the Cave Story style lava.
But the cool thing about using my main character is the fact that I can use the 3 brown shades in Marios pallete to let different levels have different palletes for the character, cave levels have a generally darker tone, or bluish tone, hotter areas (Like a lava cave or something) have a reddish tone, normal areas have the regular brown colors, etc.