Improved VFX (bullets & deaths)

[Greenfoot5]

Currently, many effects use basic shapes in an explosion shape. This is ok, but it's basic. An improvement on the VFX of both bullet impacts as well as enemy deaths. This is separate from their coin explosion effect, as that would be changed with #102. I'm not sure if different death effects are needed per enemy, maybe just bosses should get them.

There's a lot of freedom with this task as I don't have much guidence. A turret shoot effect may also be needed, but that can be discussed in #85.