There are some interesting and for most (casual) players probably hidden things in the game:

• ELEVATOR KEYBOARD CODES/CHEATS I found until now:
  
  • Type 666 for a quite good (!) horror experience: A giant spider with its children, horror clowns sawing off your plank, being buried by these clowns later when you fall off the plank, a horror clown using an electric drill to drill holes in your mouth/head.
    
  • Type 112 (which is the german phone code for calling Fire Fighters ^^) to instantly get two jets in your hands. Instant FREE FLIGHT MODE! Including gravity! This way you can go fly round the city without the annoying fire smoke and loud alarm sound. And you can survive a plank downfall.
• You can sit on the truck and the bus and drive around on them. (Around the block... literally =D Well, cool when extinguishing the fire on that one car driving behind the truck...)
  
• You can pour the fire extinguisher water on grass ground to grow flowers. Some flower types grow 5 meters high and more. Just continue pouring water on them to get them rediculously big =D
  
• Visit the football field with the giant football in the west of the city. You can score goals.
  
• You can grow pumpkins south of the city. There is one field with one pumpkin on it. Pour water on that pumpkin or that field in general and watch pumpkins in rediculous numbers spawn out of the ground; sometimes in sets of four at a time.
  
• There are cartons/boxes stacked on some buildings. You can throw them down by hitting them with a little speed (full two jet speed from 5 meters is enough) to collapse the stack and let it fall down. The collision detection reacts on jet and box. So put your jets together and hit your target with them. The boxes will fly around... Haven't figured for now whether and what secret about that is. I thought mayber all boxes must hit the ground. Maybe I didn't find all of them...

And in general: Don't hit hittable objects (helicopter, giant football) and solid level walls & ground too fast, or you will DIE :) Very good developer choice!!! The engine calculates this collision mechanic all the time. (The death by falling off the plank is one consequence of it.)

Funny stuff! Makes the game really good for a more sophisticated and replayable VR experience.