Air Theremin — play a theremin with motion or bare hands

Play it in mid-air, two ways. HANDS — wave both hands at the camera: spread them apart for volume, raise them for pitch, lean back to soften the tone, put your palms together for silence. A laptop webcam does just as well as a phone. GYRO — on a phone, tilt it instead: left-right sets volume, forward-back sets pitch, and the whole range lives inside the frame (tilt the marker outside it to cut the sound). With neither sensor nor camera, the mouse drives it. Press START — on a phone, hold it steady and it calibrates to your grip.