Rube-Goldberg project ideas/help?

well you could start the line with gravitational potential energy by holding something and dropping it on something too start the reaction... or have it hang from a piece of string and cut the string too let the thing go. that's just some advice cause that will probably be the hardest thing too put in the project. the rest of it improvise... go on youtube and find some chain reactions people have done for some inspiration also the reflection and refraction you could have a strong beam shine on a mirror then the reflected light to go through a prism for refraction then absorbed by a solar panel... if you just have design the project then you could use that but if you have too make it then that isn't a great idea cause it would be difficult and expensive