Ragdoll physics! Friendly fire! Connectivity issues! On-the-nose satire! Bugs! Double-A gaming is back, baby. You could argue it never really went anywhere, but still: what a breath of fresh air this one's proven to be.
"This is also the latest game from Magicka developer Arrowhead Game Studios - a studio, right, whose logo. In other words, you should expect a few quirks. The biggest of these is friendly fire: it is so terribly easy to shoot your own team-mates in Helldivers. It's so terribly easy to be shot by your own team-mates. Or stepped on by them if they've unlocked mechs. Hell really is other people.
A final ingredient in the special sauce though, I reckon, is the fact that so little of this is ever explicitly explained. Helldivers 2 has a good tutorial - I left it knowing how to duck and dive and successfully shoot my gun - but after that you're on your own, a glove-like fit for it's ridiculous space-jingoist theme of sending fresh patriots out to die, but also a little stroke of genius, I suspect.