its not too early. We just had day 28 horde and got them for the first time. We used concrete and traps to make a base and it worked fine even with one getting to us and blowing up. You can easily see them from far away, shoot their chest and they blow up at a safe distance. We could have had this base day 21 but we were being lazy and screwing around a lot lol we used a ramp base before that and it probably would have worked well against them.
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it has a giant green light on it's chest, its pretty easy to spot
Bear in mind different people play with different brightness settings. Personally as someone's who's been out away from streetlights after sundown with a partial moon i find the default way too dark on a night. But my relative i play with insists on sticking to defaults and he can't see anything till it steps into a strong light source. If he doesn't have that they can be beating on iron bars he's stood up against and he's only 50/50 odds on seeing them.