Press the arrow keys to go what direction you want. Hold them to continue in that direction. Do nothing to go straight. (Note: You can't go diagonal and turbo mode creates a blank rail.) For a better experience: go full screen, block/turn-off any light source (like windows or lights), make the computer eye level. For the BEST experience: do the better experience plus sit in box which should be on something safe, stable and flexible (like a giant beanbag) so you can rock back and forth
I added different speeds. Credit to @ScratchStang for the original project. I couldn't add my username to the thumbnail because it kept crashing for no reason when I started typing in the costume editor.