Some progress: https://denischera.com/reactor_defence2/index.html
For now you can just add some money with 'space' and upgrade 1 state of reactor, clicking on it :) But in general it's not playable yet, just mobs moving through all the floors.
By the way, that's REALLY huge disadvantage that Defold has no built in function of selecting objects by clicking on them. For now, I am kinda not sure how to realize upgrading not only reactor, but other objects (turrets, etc) :(