Stamina for physical actions (Jumps and crouching). This problem exists in every arcade shooter. But spamming jump and crouch gives an unintended advantage. To fix this I suggest to add physical actions stamina. The more you do these actions, the less effective they become. Jumps become lower, crouch/standup become slower. And effect should be noticeable from the second iteration. All physical actions uses same stamina value, it will prevent tactics like Jump->Crouch->Jump->Crouch. IRL crouching shouldn't be affected, but also should waste stamina