Zomba is a game about a military "Yuri" who got into a zombie apocalypse. You need to fend off multiple zombie attacks. Shoot and buy new weapons in the store. But if the lives drop below 60%, you can use the first-aid kit (R or click on the first-aid kit). Also, in the weapon, the cartridges are not infinite, to reload them, press the RMB (there are 0 cartridges).