The Sierpinski triangle is one of the most commonly-seen and easily-constructed fractals, but there’s no reason it needs to stay flat. The same construction applied on a tetrahedron results in an object that’s very predictable, but is still a little tricky to fully grasp without seeing it from a handful of angles.
What’s really interesting here is less the fractal and more the technique used to render it — raymarching, an uncommon algorithm that seems tailor-made for 3D fractals. It’s simple to write, makes detailed images, and runs fast enough to render in real time. If you find yourself interested in this sort of fractal, researching raymarching is the place to start.
Drag on the scene to look around. If you have a keyboard, you can use WASD to move around and hold shift to move faster. On a touchscreen, you can also hold with two fingers to move forward and three to move back.