Great idea! So maybe like a traffic light will work too? red while the spike is exposed, green when it is hidden in the ground and yellow when it is about to deployed.
Edit: Oh well, just realized that kinda break the monochrome style. Timer will work too, but I felt like the area with a lot of spikes/hazard will have a ton of timer, making the screen looks kinda hectic? Will have to try it out and see if it looks good.