RIGHT ANGLES IN NATURE CAN APPEAR DUE TO GRAVITY, AS A RESULT OF SYMMETRY OF SPACE. Objects fall under force of gravity vertically, i.e., perpendicular to the horizon, which is a level of gravitational equilibrium (equipotential surface).

Trees grow perpendicular to the ground

When two billiard balls collide they diverge in two directions forming right angle with each other. Try with coins of equal mass (denominations) on a table and carefully watch the angle

Right angles appear also in crystal structures. As a sophisticated example see the Archimedean Snub Cube. It has even square faces.