Maser

The first thing user notices is the image and they get an option to guess the hidden prompt behind the image
Here i've guessed the prompt and AI gave score to my comment out of 100, if scored above 85 you get to create next round of image
New round starts every 4 hours
Live leaderboard and user gets XP for each guess

Maser – the AI hides a prompt and Redditors reverse-engineers it

Inspiration

Maser started with a simple thought: every AI-generated image begins with a prompt that nobody ever sees.

That hidden prompt felt like the perfect guessing game. Players see the image and try to figure out what prompt created it, while AI scores how close they were.

We also took inspiration from Wordle, not just the puzzle itself, but the habit it created. Daily challenges, streaks, and friendly competition keep people coming back, and we wanted to bring that same experience to Reddit.

What it does

Maser is an AI-powered daily game built for Reddit.

Each round, Gemini creates a hidden prompt and generates an image from it. Players study the image and leave their best guess in the comments.

Gemini compares every guess with the original prompt, scores it from 0–100, and replies with funny hints and feedback. If someone scores 85 or higher, they successfully crack the prompt.

To keep players engaged, Maser includes the following:

Daily puzzles with streaks
XP and weekly leaderboards
Winner flairs for top players
Automatic 4-hour rounds
Live score updates
Reddit DMs when a round ends

The Reddit comment section becomes the game itself.

How we built it

We built Maser as a TypeScript monorepo using a clean architecture so the game logic stays independent from Reddit and AI services.

The core game engine handles scoring, streaks, XP, attempts, and progression, while the Devvit app connects everything to Reddit.

Gemini powers both the game creation and judging:

Generates the hidden prompts
Creates the images
Scores player guesses
Writes contextual feedback

Redis powers leaderboards, player progression, streaks, and live game state, while scheduled jobs automate image generation, round transitions, score updates, and player notifications.

Challenges we ran into

The biggest challenge was working within Devvit's runtime.

Since background tasks can't simply run after a request finishes, we moved long-running operations like image generation, score updates, and round transitions into scheduled jobs.

We also couldn't use the Gemini SDK directly because of runtime restrictions, so we built our own lightweight REST client.

Supporting Reddit's different mobile and desktop clients also required multiple UI adjustments, especially around scrolling, webviews, and responsive layouts.

Finally, because guesses are public comments, we used Reddit's spoiler formatting so players can discuss the game without immediately revealing the answers.

Accomplishments that we're proud of

Built a fully automated AI game that can continuously run inside a subreddit.
Used Gemini for both generating content and judging players instead of relying on fixed answers.
Turned Reddit comments into the primary gameplay mechanic.
Added streaks, XP, leaderboards, winner flairs, and live updates to encourage players to return every day.
Designed the architecture so the game engine is independent, testable, and easy to extend.

What we learned

We learned that building a fun game is only half the challenge.

The harder part is giving players a reason to come back tomorrow. Features like streaks, seasons, and timely reminders ended up being just as important as the gameplay itself.

We also learnt how valuable clean architecture is even under hackathon time pressure. Separating the game engine from Reddit-specific code made it much easier to iterate as the project evolved.