It was an old defense style game where animals (maybe monsters also) would come from the right and you would stop them from reaching the left side of the screen. It was set up in a town with the main weapon guns. Some things I remember:
- You could headshot the animals for more damage
- Depending on your weapon, your crosshair would grow in size based on how far from the left you were aiming and the shot would land randomly inside the crosshair.
- You could hire NPCs which would have the same aiming mechanic. You could see their crosshair moving, get bigger/smaller, and you could also set the NPCs to prioritize target animals depending on their weapon's better range to shoot
- There might have been a level up/skill/perks system that rewarded you for using the same type of weapons.