Idea for extended mortar:
I'm gonna need two variables to help explain, x [a.k.a minimum range] and y [a.k.a maximum range]
By using 3d physics, the mortar shoots a projectile at different speeds, at an arc. Due to using an arc, the extended mortar cannot shoot anything from range 0 to x, and y to inf. However, the extended mortar can shoot between distances x and y.
Oh, it can't go up very many levels of land, either. Unless it has projectiles which go through the ground or something like that.
Unusable as a front-line weapon, but a line of these teamed with a line of blasters or many mortars can attack enemies from far away.
Also, the waves made from this are "weaker" than the mortar waves because of 3d physics: the creeper is trying to spread out while at the same time trying to go as a "wave" - therefore, the wave shrinks [?] in size as it progresses towards the target.