Edit the variables (2 is the right Castle), and then click space to shoot! For those physicists out there, regarding the first castle, the origin is in the middle. x0 and y0 are -150 from the origin. Point final (x y, or x0 y0 for the second castle) are (150,-150). Half Gravity is standard 4.9 pixels /s^2.
Thank you for the Explosion Sprite, @JOEJOE2. Thank you, my Physics Teachers, for teaching me Kinematics.