Design Statement
The theme track felt like a loop that keeps building: the same phrase returns, each time with more layered on top, until it swells into the drop. We turned that feeling into the core rule of the game: one 60-second song, played again and again, and every attempt you make stays in the song with you.

You fight a Core that attacks strictly on the beat. Alone you can't beat it, but when the loop rewinds your last run replays as a cyan echo, shooting exactly where you shot. Like instruments joining an arrangement, up to five versions of you stack up until the Core breaks.

Key choices: every attack is a pure function of song time, so echoes always stay valid and the song stays the same each loop. The drop at 0:21.5 opens the Core's weak point, so the music's big moment is also the gameplay climax. Shots snap to 16th notes and hits sound in a pentatonic scale, so even your damage plays along. We kept the visuals calm and vector-only so the track stays in front, and the music is used unmodified.

Game Instructions (launch steps, controls, and gameplay overview)
Browser: press Run game, then Start fighting (click needed to enable sound). Windows: unzip ECHO60-2.4.0-x64.zip and run ECHO60.exe.

Controls: WASD / arrows - move; mouse - aim; LMB / Space - fire; R - end the attempt and rewind; Backspace - remove the latest echo; T - damage assist (offered after 4 attempts on a boss); Esc - pause; M - mute; F11 - fullscreen.

Gameplay: each boss fight is one 60-second loop of the theme. Dodge the beat-synced attacks and shoot the Core. When the song ends or you press R, time rewinds and your previous attempt fights beside you as an echo. Stack echoes (up to 5) and break the Core; the drop at 0:21.5 opens its weak point for double damage. 5 bosses, about 15 minutes. A "Reduce flashing & motion" option is on the title screen and in the pause menu.

Gameplay walkthrough video
https://youtu.be/sEhXYf9AU-w

Did your project use any AI tools or assets? If yes, please specify.
Yes. Code was written with OpenAI Codex; game design, balance, texts and code review were done with Anthropic Claude; a human producer directed the project and playtested it. Early concept art was AI-generated but is not in the final game, which uses only code-drawn vector graphics. The music is the jam theme by Jason Grace, unmodified; no AI audio.