what puzzle game is this?

there's a puzzle game i really like, but i can't remember what it was called so i can't find it anywhere to play it again. i always called it pearls and oysters, but i guess that's not it.

the game has black and white circles on a grid. the goal of the game is to make one, unbroken loop that goes through all the circles while fulfilling the requirements that each color has; the line must bend at at least one end after going through a white circle, and the line must go straight for two squares when going through a black circle, making an L shape with the corner being where the line hits the circle.