I'm amazed how fast you were able to replicate original Mario Bros. Gob is harder though, especially castle was much more intense.
For a small game there's not much that I can add as I think it's feature complete. there are some minor things that could be improved.
Secret room is a dead end, hidden block or exit would be appreciated, otherwise you have to wait till the timer ticks down.
After you die your coin counter resets, that's not how Mario games operate. Moving platforms change direction instantly and they should slow down first, it makes these jumps much more difficult.
Small game window and control scheme. Your game could *really* benefit from adding an option to have left shift for jump... Just kidding, but rebindable keys and resizable window/fullscreen is pretty important.
With the bugs, I died when two enemies were close to each other, stomping at them both killed one and second killed me in the same time.
I found a blind spot - when jumping you can hit a block but you wil not destroy it.
Anyway, great game! I actually like your take with goblin attacking dwarf fortresses. You can expand it and make more interactions, maybe a bigger castle? I'd experiment with the concept a little more, there is a hidden potential here.