What they are
Level 1, the standard Rocket Propultion System. "Significantly increases you acceleration" These rockets provide a little boost to your Taxi and are breakable. This upgrade becomes available at shop level 5 and costs 2,500$
Level 2, indestructo-Rockets. These rockets provide a little boost to your Taxi. They are unbreakable and have a Grey texture. "Rockets made of a material so strong that they never break" They cost 10,000$ and are unlocked at Shop level 7.
Level 3, Nuclear Reactor Rockets. "Goes really fast... as long as you don't mind a little radiation poisoning" These rockets provide more boost to your Taxi than the previous two levels. They are unbreakable and have a new texture. They cost 50,000$ and are unlocks at Shop level 8.
Level 4, Guestium Rockets. These rockets are VERY fast. They can make almost any Taxi fly. It is the last level. they are unbreakable and have a new texture. They cost 1,000,000$
- The level 4 rockets have 1 pixel of guestium in them, preventing it from scaling strength.
- The blue parts on the level 4 rockets are just paint.