Test-particle orbits (left col.) and energy gains (right col.) vs. z-coordinate (blue lines), obtained during the same running simulation time, Δt = 8×10⁻⁵ s for: panel a: magnetized electron in the magnetic island described by Eqs. (14) and (16) with B₀ = 100 G and the guiding field B_y = 0; panel b: unmagnetized electron in the magnetic island with the same dimension as panel a and B₀ = 10 G; panel c: magnetized electron in the magnetic island which has the same B_x and B_z components as panel a with added guiding field B_y = B_z0 ξ, where ξ_y = 0.1; panel d: magnetized electron in the magnetic island which has the same B_x and B_z components as panels a and c but with a stronger guiding field, ξ_y = 1.0; and panel e: electron in the magnetic island which has the same magnetic field topology as panel a for the electric field following Eq. (17) representing squashed islands. The magnetic field lines of B_x, B_z are plotted in orange lines for all cases. Here k = 0.03125, ϵ = 0.3.