Thanks for reporting this. =)
Thats intended. Its more related to old NES, Sega game logic/controls. Pressing up usually means entering/activating something in sidescrollers. But true it might be confusing, I might change it to down button. What comes to stairs I wanted to keep it like in the original Simons Quest. I could have just done it the same way as diagonal blocks function in the game. Just a matter of preference. But yes if you think it should be press down I could change that for next version (if i remember to do so). But as for the stairs there are not too many of them so I might not change it to the just walking slopes option but we shall see. But I can tell you its harder the way I did it, more so matching the walking animation with the stairs.
EDIT: after testing I remembered why its not donwards key. You cant crouch in many situations, and get extra hits for accidental stair access.
Next update has gotten alot bigger than I expected but its almost done. Next version will include (in short): New enemies, new areas, redid the whole lost castle, second boss finaly done properly, new effects, new animations, A LOT OF FIXES, improved menu controls, improved graphics, quality of life fixes (asking if overwrite, screen centering after changing screen size, etc). I might be able to get it out tomorrow. Still have to make one more area, make short cut out of a certain place and maybe add petrified status (the same effect from a game like Castlevania: SOTN).
Thanks for the info and feel free to inform any oddities, weirdness and such.