Rover Builder update - Sandbox mode with rockets

We just shipped an update! Here's what's new:

Sandbox Mode:

• A brand new mode that you can find in the mission menu (in the player information box)
  
• White, flat and clean environment for testing designs without having to start a mission everytime
  
• New Rocket part in the sandbox mode! Pretty self-explanatory, a part that provides thrust with Space key by default. As of now you can't use this in the existing planets, there will be a rocket planet in the future. We just wanted to already let you play with it in the Sandbox :) In the missions rockets will have limited fuel, but Sandbox has infinite fuel.
  
• "Drop a box" -feature that drops a random box behind the rover, so that you can easily test lifters
  
• Sandbox mode is also ideal for stylish screencasts!
  

UI / Usability features: