Unseen Echoes

Inspiration

What would a game feel like if you had to understand the world primarily through sound?

That question became the starting point for Unseen Echoes. We wanted footsteps, distant voices, and sounds behind doors to become information that players could act on. Listening would shape how they explored, survived, and solved a mystery.

The investigation also draws inspiration from Edgar Allan Poe’s The Murders in the Rue Morgue: people can hear the same sound, describe it honestly, and still reach different conclusions. We wanted players to experience that gap between hearing something and understanding it.

What it does

Unseen Echoes is an audio-first browser adventure that takes players through three connected experiences:

Learn to navigate by sound. A tutorial introduces spatial listening through environmental sounds that change as players move and turn.
Survive a multiplayer chase. Two players become a hunter and a survivor. The hunter listens for the survivor’s heartbeat, while the survivor uses the hunter’s footsteps to judge danger and find a way out.
Investigate a hotel mystery. Players explore Pinewood Inn, question witnesses, find a recording, and compare what people believe they heard with the available evidence. AI conversations let players ask questions in their own words.
Another Door. Describe a new world. Gemini creates a validated, bilingual four-room setting using the existing sound library.

Across these experiences, sound becomes a guide, a warning, and a piece of evidence.

How we built it

We built the browser experience with HTML, CSS, and JavaScript, using the Web Audio API for spatial sound. Direction, distance, and—in the exploration scenes—doors and stairs affect how players hear their surroundings.

SpacetimeDB synchronizes the multiplayer chase and manages shared game state. Gemini supports character conversations and evaluates players’ explanations in the investigation, while ElevenLabs provides spoken responses.

We separated fixed game rules from AI dialogue. Movement, evidence collection, and progression follow explicit rules, while conversations use character knowledge and discovered evidence as context. This gave us a defined mystery to build around while allowing players to explore it through natural language.

Challenges we ran into

Our biggest challenge was time management, especially early in the hackathon. We changed ideas too many times, and each change took time away from implementation, integration, and testing.

We initially spent too much time imagining what an exciting project could look like before checking whether its central features were technically achievable. Some ideas depended on capabilities we could not make reliable with the available tools and time.

We had to become more disciplined: identify the essential experience, test the hardest assumption early, and commit to a scope we could actually build.

Accomplishments that we're proud of

We are proud of turning an unusual interaction idea into a playable browser experience that combines spatial audio, multiplayer tension, and AI-supported investigation.

The same act—listening—serves different purposes throughout the game. Players first learn where a sound comes from, then use it to anticipate another player’s actions, and finally question what it means.

We are also proud that, after several changes in direction, we brought these parts together into a connected experience.

What we learned

We learned to evaluate ideas from an engineering perspective: what capabilities they require, which parts existing tools can support reliably, and which assumptions need a small prototype before further investment.

We also developed a more realistic understanding of current technology. Powerful models and APIs still have limits. An impressive individual result does not guarantee the consistency, precision, or responsiveness that an interactive experience needs.

Most importantly, we learned to let technical evidence shape our ambition. Testing feasibility early helps us choose where to be creative, where to simplify, and where to spend our limited time.