Finally managed to get the true ending! To be honest, this game was kind of a letdown at launch, with it being way too difficult for my smooth brain to get any enjoyment out of. But coming back to it recently, they've added a ton of ways to tinker with the difficulty, and as a result it's incredibly addicting now! There's a ton to unlock too, from new ways to play to cosmetics, so I'll continue playing this for a while.
Speaking of cosmetics, this game looks fantastic, and the music may be Jake Kaufman's best work since Mighty Switch Force!