The tarp used in this project is a touch pricey (around $15); if that’s a problem, feel free to replace it with several cotton sheets (which you can usually get at the Salvation Army for a buck or two per). The sheets will be easier to cut and sew but won’t hold up to the weather or block out light as well as the canvas; 3/8 of the coolness factor of any play tent is the degree to which it is dark and cozy, like a little animal’s den.