Gainer is a toolkit for physical computing that consists of an I/O module and software libraries. The I/O module is designed for use with breadboards and uses a PSoC microcontroller with built-in op-amps and reconfigurable ports. It comes with multi-platform software libraries for Flash, Processing, and Max/MSP that are open source under a BSD license. The goal of Gainer is to lower the barrier to entry for physical computing education and projects.