Hi HawkZombie, thanks for the feedback!
Spike trap can be set with this: once you got the spike selected, press down constantly with left mouse key at the position you want to set the trap at. Then while pressing left mouse key down, press SPACE at one of those three tiles in which those traps can be placed. In that first section where Spikes had to be placed on the road where those mannequins walk, there are only three tiles where that is possible.
I am sad to see that being unable to save was the case. For some reason as I developed the game a bug of saving game came into action and this it gives an error if you try using F12. I simply cannot tell why that is, I did use the basic MV save system without any plugin going against it. Unfortunately I could not remove that in time as it came to be within last day. If you don't save or reload, it should work without a hitch.
Hopefully this helps. Making the system from the ground-up was a challenge and is definitely going to be made smoother as the time goes on. Whatever happens in the competition, I am going to develop and release this fully.