koturn's shader 2D arts for GLSL.
$$
f(x, y) = \dfrac{|x^2 + y^2 - 2(x + y) - 10| + x + y - 5}{\max \left(|x|, |y| \right) + 3 \left| |x| - |y| \right| - \dfrac{3}{2}}
$$
$$
r(\theta) = \dfrac{3}{4} \min \left( \left| \cos \dfrac{5}{2} \theta \right| + \dfrac{2}{5}, \left| \sin \dfrac{5}{2} \theta \right| + 1.0 \right)
$$
This software is released under the MIT License, see LICENSE.