The Roller Dome

Link two mechanics so one feeds the other, like tricks refilling ammo. Paul Rabbitte made The Roller Dome in 48 hours for the 2017 GMTK Game Jam, themed "Dual Purpose Design": a top-down twin-stick shooter on rollerskates where doing tricks gives you ammo for shooting.

He had wanted a movement-shooter premise, but his other ideas felt forced, and he called the trick-and-shoot link a natural fit. In the final Rollerdrome, grabs and grinds still refill ammo. Quote: "what if it was Tony Hawk style movements but doing tricks gave you ammo to link into the shooting side of it."

A rough jam entry is a seed; keep the core idea and rebuild. The jam entry was fiddly and crazy hard, but the core idea held. Rabbitte remade it in 3D, and GIFs of the remake went viral on Twitter, drawing publishers and leading him to Roll7, the team behind OlliOlli.

He was a freelance developer making solo projects and jam games in his spare time; Roll7 gave him a team of artists and designers to build the full game. Quote: "a game jam game is usually just the kernel of an idea. A seed."

Cut features from both genres so players think about one thing. The first literal mix of Tony Hawk's Pro Skater and DOOM 2016 was an overwhelming mess, with two games fighting for the player's attention. The team made movement automatic, removed bailing and the grind balancing mini-game, shared ammo, gave early weapons auto-aim and kept most enemies stationary.

Reflex mode adds slow motion at a button press, and quarter pipes around the arena shove you back in even if you aren't looking. The team iterated until the combination felt most natural.

Move difficulty into enemies and hazards to keep the intended intensity. With mechanical friction removed, challenge shifted to enemy variety and hazards like laser beams, poison puddles and stomping mech walkers, so it still feels like a dangerous bloodsport.

Rabbitte said the aim was "this super high intensity thing," and that feeling guided every cut.

Reward risky timing on existing verbs to add depth without new buttons. A dodge at the last moment before damage is a "perfect dodge"; entering reflex mode after it triggers "super reflex", which boosts attack power and turns the dodge from defence into offence.

It grew from a prototype quirk where well-timed dodges clipped through enemies unharmed; Bayonetta's witch time inspired rewarding that risk, and a bonus on the existing reflex mechanic was the easiest reward. Designer Drew: attacks that once terrified you become an asset, "I'm gonna skate into that landmine or that rocket."

Gate progress on skill challenges so players grow from prey to predator. New levels unlock only by clearing bonus challenges, such as high scores that demand intention, using guns against weak enemy types, and super reflex.

Returning to early levels where you once barely survived, you now blitz your old high score. Drew: "You are whooping ass in those earlier levels, and you see how much you have progressed."

Superhot, Baba Is You and others also grew from jam games. Superhot came from 7 Day FPS, Titan Souls from Ludum Dare, Baba Is You from Nordic Game Jam, and Keep Talking and Nobody Explodes from Global Game Jam.