The applet below plots the curve |d₀+d₁u₁+d₂u₂|=1 on the torus |u₁|=|u₂|=1. The coordinates are t_j where u_j=e^{2&pi i t_j}, so that the torus is represented as a square [-0.5,0.5]x[-0.5,0.5].

The buttons allow to change the parameters d_i.