This is one I grew up with (as the dart & square plane alternative). If you fold the winglets as the instructions, you end up with an aerobatic plane. If you instead just gently bend the plane in half along the center line (so it looks somewhat arc-shaped), you get a pretty reliable glider.
As a kid, I only knew the basic design and the square. I almost always used the square, which I learned with two differences from the description on the website: I folded up the outer ~0.5-1cm of the wings as "winglets" (which seemed to help stability) and folded in a triangle of varying size in the back of the fuselage for trim instead of cutting ailerons into the wings.
On a windy day in the vortices behind trees at my elementary school bus stop, I had such a square glide for what felt like at least half a minute (unreliable narrator obviously) after launching to maybe 3-4 meters. That lucky random walk wouldn't have worked without the low sink rate of a good square.
https://www.instructables.com/id/How-to-make-an-aerobatic-pa...