LTspice is a high performance SPICE simulator, schematic capture and waveform viewer with an impressive library of passive devices. Over 1000 models are included in the download but you can also add third party models.
Control LEDs based on your movement using an accelerometer! Make your LEDs breathe by fading in and out when laying on the floor, turn off the LEDs when moving to your side, or make the LEDs blink in a headstand!