Take a side-scrolling stroll through this week's PlayStation Store update, which adds Mercenary Kings and a Batman Arkham spin-off to the aisles.

Mercenary Kings, a thick-set Metal Slug-esque shooter with wild animation, comes to the PlayStation 4 in the same footsteps as survival game Don't Starve: from Steam's Early Access on PC, to completed freebie through PlayStation Plus (and $20 otherwise).

Meanwhile, Batman: Arkham City for PlayStation 3 enters the Plus library as a free download. The 2.5D spin-off of Batman: Arkham Origins, dubbed Blackgate Deluxe Edition, is also in store for $20, having transitioned from Vita and Nintendo 3DS to this updated PS3 incarnation.

Check PlayStation blog for the other updates and convoluted titles, including Shin Megami Tensei: Devil Summoner: Raidou Kuzunoha Vs The Soulless Army. That's the one with Grigori Rasputin.