The act of simply completing Dark Souls, the notoriously difficult action role-playing game by From Software, is for many players an impressive accomplishment in and of itself. But player Benjamin "Bearzly" Gwin took the Dark Souls challenge to another level: He beat the game using nothing but a Rock Band guitar controller.

Gwin recently completed his "Guitar Souls" run of the game with a custom input mapping for the Rock Band Xbox 360 controller, which he detailed on Reddit. He says he mapped many of the Windows PC game's inputs to the guitar controller's fret buttons, whammy bar, effects switch and "star power" detector. The limited control options meant that character movement was restricted to forward, backward and right, and camera control was restricted to panning left. It also meant he couldn't block or use heavy attacks.

According to Gwin, his guitar controller Dark Souls run took a little over 11 hours and — not surprisingly — areas like Sen's Fortress and bosses Ornstein and Smough were some of the most challenging parts of the play-through. The game's final boss — Gwyn, Lord of Cinder — proved easier than expected. That fight only took three attempts, he said, as Gwyn was kind enough to repeatedly attack with a move that's easily parried for his final fight.

Gwin's strategy for surviving boss fights with limited controls appears to have been to don the heavy Havel armor set and stick to the halberd, which has good reach. At some points, he plays mostly naked for speed. He's posted some highlights from his live Twitch play-through to his channel, including this nail-biting encounter with the Anor Londo archers and his trip through the trap-laden Sen's Fortress.

Beating Dark Souls under unusual circumstances isn't new for Gwin, apparently. He also played the game one-handed in a separate run. His next challenge, he says, is tackling Dark Souls 2 with a guitar controller.

Here's a look at Gwin's successful fight against Ornstein and Smough.