Yesterday I wrote about Potion Pile and Nine Heavens Ascent, two mobile games I shipped to the App Store and Google Play using vbgnt. Both were straightforward projects: a single-screen physics merge puzzle and a 2D idle game built on menus and timers. They were tidy, they worked well, and they proved out the pipeline from a text prompt to an app store listing.
Claude Opus 5.5 is now in vbgnt's model picker, and the scope of what comes out jumped immediately. The first three games I built with it are much larger in scale and mechanical complexity. Each one started from a single written prompt, followed by a handful of follow-up notes after I played the early builds. The studio plays every build in a headless browser on desktop and phone before handing it back, which catches control and viewport problems before you ever test the link.
Kartropolis
I asked for a 3D superhero kart racer where characters race through cities during alien invasions and supervillain attacks. The brief asked for Mario Kart style power-ups, an ult meter filled by drifting, passing, dodging, and landing hits, a boss arena after every race, a bright animated-film look, and voiced catchphrases.
The first build came back with four original heroes: Captain Comet, Volt Vixen, Titan Tess, and Frostbyte. Each had voice lines and an ultimate ability. It also built two tracks. Downtown Invasion sends racers down city avenues while alien saucers fire lasers at the road and a mothership hovers overhead. Harbor Havoc takes place at sunset against bomber drones and a giant robot standing in the bay. Crossing the finish line drops all four racers into a boss fight against The Overmind or The Mega-Bot. It included Homing Rockets, Goo Bombs, Turbos, Force Shields, three-stage drift sparks, two-player split screen, and controls for keyboard, gamepad, and phone screens.
A couple of follow-up notes were needed. In the initial build, each wheel had its pivot set below its real center, so the karts rolled down the track like eggs. Captain Comet also had strange webbing on his face and a stiff, modeled cape stuck to his back. I asked for a new model without a cape, plus a cape simulated in code. The studio replaced it with a starry indigo cloth cape that drapes over the kart when parked, streams straight out at speed, swings into turns, and glows when he hits a boost.
Play Kartropolis.
Cat Person
The brief for this one was simple: a cat lady runs down a city street collecting stray cats that stick to her body. Once she gathers enough cats, the group forms a Katamari-style ball and keeps rolling, growing bigger and bigger.
The studio built a third-person 3D roll-'em-up with ten distinct cat models: an orange tabby, a googly-eyed black cat, a grumpy Persian with a bow, a derpy Siamese, a calico, a tiny kitten, a sphynx in a sweater, and a tuxedo cat, among others. At the start, cats cling to her arms and legs, and right on top of her head. Once you collect ten cats, they swirl into a rolling ball with the cat lady running on top. From there you roll up cars, taxis, hydrants, street lamps, trees, and eventually buildings. The whole run lasts five to eight minutes, and I will not spoil what happens after you leave the pavement.
The follow-up notes on this one were about pacing and presentation. The original title screen showed the space levels, giving away the ending before anyone took a step. I asked it to pull that back. The revised cover shows the cat lady hugging cats on a sidewalk, with the menu line reading "ROLL UP EVERY CAT IN THE CITY". I also had to fix the traffic: the cars were initially driving backwards down the street, so the agent turned them around to drive headlights-first.
Play Cat Person.
Fat Bear Week
I asked for a bear simulator set on the real map of Katmai National Park. You wake from hibernation skinny, spend the summer eating to get fat for the winter, and watch your bear expand until it looks absurd. The brief asked for realistic geography mixed with humor, AI rival bears, an end-of-season tournament ranking everyone by fatness, and multiplayer later on.
The game drops you as a thin brown bear on the real Brooks River. You spend the season catching salmon at Brooks Falls, grazing on sedges, digging for clams, harvesting berries, and bullying rival bears off the gravel bars. As you eat, your bear expands outward and the HUD updates your rank from "Skin and Bones" up to "Chonk Legend". At the end of the season, Fat Bear Week ranks every bear by final weight. The game borrows its name and format from the real Fat Bear Week run by Katmai National Park and explore.org, but it has no official affiliation with them.
Multiplayer was flagged as a later goal in the initial brief, and it was added over subsequent turns. Rooms support up to eight bears using a four-letter room code, and AI rivals fill any spots humans leave open. It includes proximity voice chat that you toggle with the V key. Nearby bears can talk to each other while fishing the falls, and nobody hears you past about 55 meters. It is still early.
Play Fat Bear Week.
Where to play them
All three games play free in a browser on desktop or phone. You can plug in a controller for Kartropolis, spend five minutes rolling up a city in Cat Person, or jump into Brooks River with a friend in Fat Bear Week.
If you want to build games like these, vbgnt is the studio that made them.