Drag the particle to set initial position. Drag the small arrow to set initial velocity. Adjust field intensities live. Click the canvas to place the particle.
• Uniform fields: E is in-plane, B is along ±z. In 2D: a = (q/m)(E + v × B) with v×B = (v_y Bz, -v_x Bz).
• Use negative Bz to flip gyration direction.
• With E=0 you get cyclotron motion; with E≠0, watch the E×B drift.