30 participants each started a drawing then passed it to the person on their right upon hearing the beep. This continued until the drawings had been passed between everybody in the class forming 30 drawings made by 30 participants.

https://www.we-have-iuav.com/files/gimgs/th-79_79_p1000294.jpg
https://www.we-have-iuav.com/files/gimgs/th-79_79_p1000290.jpg
https://www.we-have-iuav.com/files/gimgs/th-79_79_p1000286.jpg
https://www.we-have-iuav.com/files/gimgs/th-79_79_p1000282.jpg