Can anyone tell me how to flip a sprite horizontally? The only thing I could find was SPDEF, and the manual isn't helping.

SPCHR with the attribute #SPREVH will flip a sprite horizontally. SPCHR 0,,,#SPREVH See more here http://smilebasic.com/en/reference/

Thanks! Also, how do collisions work, exactly? It's so easy in GM:S, but so hard here!