Create a tablet app script with a single button that turns it on and off (as with Fingerpaint). When the 'clap' button is on, moving your hands toward each other (meaning that the palms are facing each other with an angle difference of less than 45 degress) will cause a clapping sound to be made, along with a particle system of briefly fading 'sparks'. The trigger for the clap sound and particles is the hands approaching each other and crossing a distance of less than 30cm (adjusted by the avatar's scale, so that this still works if you are scaled up or down). The velocity of the hands at this moment should scale the loudness of the clap sound, as well as the max radius and number of particles. The clap sound should be randomly chosen from one of 5 different samples, so that repeated clapping does not sound repetitive, due to both the changes in volume and the difference in chosen clip.