An improved "rebound selection" simulation constructs a polymer chain in biased excluded volume avoiding steps. A construction that in midcourse accumulates a low bias weight tends to be arrested by a selection. Conversely a high weight construction sprouts reserve bifurcation and if subsequently it is arrested, it falls back and rebounds from such bifurcations. The simulation is applied to a condensation transition of thermal 2d lattice chains, and to a dilute-semidilute transition of athermal chains. Semidilute 2d chains do not mix, 3d ones mix as blobs.