Stand still and take the fight, choose a teammate to add a shield after death, and then choose a zombie to kill and add a teammate to increase the maximum limit of teammates (these three are the main upgrades). For others, you can choose lightning bullets, flamethrowers, Just wait for the mines to replenish the damage. Leveling up one will have a strong effect. I can't even fight the BOSS. When the shield is leveled up, a teammate will be invincible for six seconds. With the shotgun for all members, up to two teammates will be killed immediately. Full second BOSS
sea breeze and blue sky
One more thing, when the talent of teammate death causing explosion is maxed out, basically no monsters can appear on the screen. You still have to choose teammate death to add shield, kill zombies and recruit these.