Cool game! I think it followed the theme well as you have to make sure nothing goes wrong with the core. The first two times I played and spilled the coffee. At first, I struggled to figure out what I was supposed to do. On the third play I ignored the coffee and then understood what the dials and blocks meant if I were to spill the coffee. At that point I decided to spill the coffee and the game got more interesting managing the shapes and dials. I played a 4th time to see how the game plays if you never spill the coffee and you can infact play all the way through with out spilling the coffee (As the decription says, a very boring shift). The voice bugging you about the coffee was a funny touch.
I found the count down number started going negitive, I would imagne a polished version of the game would have that end the shift.
I will say, I kind of think the game should have just forced you to drink the coffee to stay awake. If you don't then you would dose off and wake up to the core exploding. However, on maybe the third or so time you're forced to drink the coffee THEN you would spill it forcing the game into the harder mode. Just a suggestion, great work!
If you're intrested, check out my submission "Steer Clear". It kind of has a similar vibe of managing something that is supposed to be automated but goes wrong.