In recent years, gesture-based interaction methods are supported by a wide variety of devices, such as capacitive trackpads and capacitive 3D gesture recognition systems. When interacting with such proximity-sensing surfaces, users face the challenge that the supported gestures are not directly apparent. Rainbowfish tackles this problem by combining a semi-transparent capacitive proximity-sensing surface with an LED array. The LEDs are used to visually indicate possible gestural movements and provide feedback on the current interaction status. Aside from computer-centered interaction, Rainbowfish can be used as a low-cost gesture recognition system for home automation, for example as a gesture-controllable door opener.