Do you realize the lag it would case? You would have to change the serverside properties of the projectile... Then you would have to send the new coordinates to every client.
How projectile works is that it sends a projectile with a specific height/angle/power. It sends the height/angle/power to every client while it's at it. Then the serverside projectile goes on invisible. The other projectiles are individually kept on each client (as to reduce network lag in, having CPU lag go up to compensate, share the workload!).
You will not be able to.
Now, for the exploding projectiles, yes, you can.
You can assign properties to projectiles that once they hit, they have a trigger for the projectile serverside. You can fire more projectiles when your projectiles land. Just a warning however: Don't make ever-shooting projectiles, and don't make it an exponential outcome! It'll soon become thousands of projectiles in no time.
For the mousex,mousey, use some physics of yours...
It'll requite to work out the exact power and angle to hit. The "complex" equation, is...
http://www.staff.amu.edu.pl/~romango...le-motion.html
There. It's all on that site. Read and Learn.
