Use the left and right arrow keys to rotate. Press up to move forward, and space to warp. Use 1 to toggle the sliders. change Warp Mode to 2 to enable Marker mode. Use 2 to toggle the Marker visible. Use the other sliders to adjust the percent friction and the turning speed (in degrees).
This is mostly someone else's project I found somewhere (Sorry, I don't remember the original author). I added the sliders and the ability to warp and wrap around walls. Big thanks to daemys and deck26 for helping with the marker code. see here: https://scratch.mit.edu/discuss/topic/150082 It is used to make the ship wrap the screen in straight lines. It works, but wasn't how the original asteroids screen wrapping worked.
