Overview of the binary planetesimal system in the co-moving frame. The star is located on the left side of the frame. The binary components are denoted with their masses, M₁, M₂, and radii, R₁, R₂, travelling around their barycenter in circular orbit at distance, a₁ and a₂, respectively. Pebbles are released from a distance y0 between the edges of the impact range, x₁, x₂, for a given initial phase angle of the binary, φ₀, with respect to the x-axis. The starting velocities of different pebbles differ depending on the x-coordinate as seen in Eq. (16), therefore, their velocity vectors point in different directions. The background gas headwind is denoted with the black arrow on the y-axis.