I can't fire the missile. What am I doing wrong?

Set angle in 45dg increments starting at the top and moving clockwise by using 0,1,2,3,4, etc. - every number higher is a further is 45dg clockwise. 0-360 doesn't work because variables max out at 255. You also need to get the firing behind an Every X frames block, otherwise it resets the missile position to the starting xy every frame the fire button is held.