About Spectral Horn

Spectral Horn is an optical physics puzzle by Filip Paulů that won first place overall at js13kGames 2026, a competition where the whole game must fit into 13 kilobytes. The theme was Unicorns and Rainbows, and the game takes it literally: a crystal unicorn horn works like Newton's prism.

A beam of white light hits the horn, bends and splits into a rainbow, and you have to send the right colour into each sensor. The light follows real optics: refraction, dispersion, total internal reflection and mirrors. Across 17 levels you add mirrors, a Dove prism, crystal orbs and a second horn, and even mix colours back into white light. The title screen doubles as a sandbox for free experiments.

How to play

Press Play and start with the first level.

Drag the unicorn to move it into the beam of light.

Drag the ring around the horn to turn it until the right colour reaches the sensor.

Hold the beam on every sensor until it is charged to 100%.

Controls

Drag the unicorn: move it

Drag the ring around the horn: rotate the horn

↺ and ↻ buttons: turn the horn by half a degree

Touch screen: the same with your finger

Tips

Use the step buttons for the last tiny correction of the angle.

Violet light bends the most and red the least: turn the horn to pick the colour you need.

Stuck? Reset the level from the menu at the top or pick another unlocked level.

Devices

Plays on computers, phones and tablets in any modern browser.

Similar games

Developer

License