This is the classic game Galaxy. This is a simple one player game. Place a peg in any spot. You can then place another peg at the end of any line coming out of that spot. Keep going until you can no longer fill any holes. The goal is to fill every space with a peg.
There are two versions of the board: one with a space for magnets and one without a space for magnets. There are 4 peg varieties which allow for with or without magnets and with or without an indent on top to be filled with a color.
The magnets provide a satisfying feeling while placing the pegs, though they are not necessary and were a little difficult to glue in place.
I used these magnets (cheaper if you shop around): https://amzn.to/2JWxb3j
more peg games: https://www.thingiverse.com/thing:2986808
Check out https://www.Vavtech.Etsy.com to see more stuff like this available for purchase.
Pegs should be 100% infill but the board itself can be 15%-30%.