no, not animations, visual effects, sprites and particles are needed, they may seem like minor elements but they affect the 'feel' of the game, shooting mechanics as to do with how the gun 'feels' upon fire, every gun game has a different feel, it depends on:

- gun sound effect [u have this]
- muzzle flash
- firing animation [u have this]
- tracer effect and speed/style of the tracer [alot of games tend to ignore this]
- enemy hit effect
- enemy reaction upon hit [u seem to have this]
- hit sound effect

based on how the above is done, a game can have great to terrible mechanics, ofcourse some of them are optional also