Claude Opus 5.5 and Sonnet 5.5: What They Build

Hollowdeck: a full card game, with art and music

We asked Opus 5.5 for "the next big card sensation game that's easy to learn but extremely addictive", role-playing style, played with a real deck of cards. Its first answer was a landing page for the game, so we said we wanted the game itself. A few messages later we had Hollowdeck.

It is a complete game, not a demo. The deck is a dungeon: each room deals four cards, and you pick three. Black cards are monsters, diamonds are weapons, hearts are potions and red face cards are treasure. You level up, learn perks, spend gold at a campfire between depths and fight the Void Knight at the bottom. Every card has its own illustration, generated in Looops.

Then we asked for sound effects and tavern music. Opus composed both in code, with no audio files at all, and turned the music down under the effects when we asked. There is a clock in the corner that shows how late it is getting, which says a lot about how the game plays.

Play Hollowdeck

Black Lantern: a second game from one more message

In the same project, we described a classic buy-low, sell-high trading game and asked for one "with nice graphics, more entertaining", on its own page so it would not touch Hollowdeck. Opus built Black Lantern: thirty nights to pay off a moneylender whose debt grows every night, six city districts with their own prices, a vault that thieves cannot reach, a city watch that stops you when your satchel is full, and a painted scene for every district.

Both games now live on their own sites and link to each other.

Play Black Lantern

Sizzle Pop!: a comic-book hot sauce brand, from one prompt

Games are fun, but most people come to Looops for a business website. So we wrote one detailed prompt for a small-batch hot sauce brand from Mexico City: pop art and comic books, five sauces as five superheroes, a heat scale, a four-panel comic about how the sauce is made, a fan wall and an order form styled as a comic coupon.

Opus 5.5 built all of it in one go. Thick black outlines, halftone dots, starbursts, trading cards with a power meter for each sauce, and bottle illustrations that match the style.

Open Sizzle Pop!

Same prompt, two models: Opus 5.5 and Sonnet 5.5 side by side

We gave the exact same Sizzle Pop! prompt to Sonnet 5.5. It is a fair test, because both models got the same words and the same tools.

Both results are real, working websites that follow the brief. Opus went further on type and layout: its headlines use the chunky condensed comic font we asked for, and the hero reads like a real comic panel. Sonnet drew bolder characters, turning each sauce into a cartoon hero with a face and a cape, but its headlines came out in a plainer typeface.

Our takeaway: Opus 5.5 is the one to pick when the design has to be exceptional. Sonnet 5.5 gets you most of the way, uses fewer credits, and is a strong everyday choice.

Signal/Noise: generative art for a club in a power station

Our last test was the hardest to fake: art drawn in code, different on every visit. The brief was an underground electronic music club in a 1961 power station, cyberpunk at night, with a particle flow field behind the name, a generated poster for every event, a pulsing waveform and slowly shifting static.

Opus 5.5 delivered every piece. Thousands of glowing particles drift like current and bend around your cursor. Each event poster is drawn from the event's name and date, so no two look alike, and hovering one scrambles it. A countdown ticks down to the next night, and a guest list form sits at the bottom.

Open Signal/Noise

How to use them

Open the model menu under the chat box in the builder, or on your dashboard before you start a new site, and choose Opus 5.5 or Sonnet 5.5. Both are available on the Personal and Pro plans. Stronger models use more credits per message, so a good habit is to design with Opus and make small edits with a lighter model.

Everything else works the same: your site gets real pages, forms that email you, images generated for you, and one-click publishing. What changes is how far the design goes.