Schematic overview of the simulation setup. The planet is initialised on the x-axis on a circular orbit with radius a_plan. The pebbles are released from an exterior ring with a radius of a_plan + 5R_H and slowly drift inwards. The pebbles are identified by their initial azimuthal coordinate, ϕ₀. At the start of the simulation, the collision cross-section is calculated. Pebbles released from within this region, symbolised by the red ring segment, eventually accrete onto the planet. The integration of pebbles that miss the planet is terminated once they drift past the interior ring with a radius of a_plan – 2R_H.