Click to place the block. Space to change your block type. Once you are ready to test it out, press any of the arrow keys. And that is it! Have fun!
Note: This will be updated often, as this is very new. Version 1.0.0: Original Release Version 1.1.0: Added Grid Snapping! Woohoo! Version 1.1.6: Added some music. Version 1.1.7: Added a new background. (It is just mostly for show) Thanks to @Andy8800 for the grid snapping code.