Coarse-Grained Molecular Dynamics Simulations. NVT simulations are done at constant T, constrained in 2D, and under periodic boundary conditions. Blocks are treated as rigid bodies in LAMMPS. We use a standard 12-6 LJ potential between colored beads, with σ = 1 and a cutoff of 2.3σ. The latter is used to improve the alignment of blocks as they are incorporated into the growing structure. For each simulation, all correct interactions were kept constant at a strength of ε = 1, while all incorrect interactions were set at a constant strength of ε', ε'' < ε = 1. Simulations were performed at different (T, ε') and block area concentrations ⍴ (through changing the simulation box sizes) to test if the desired target structure can be successfully assembled under those conditions. To ensure that the target structure has enough time to develop and is stable, simulations run until fluctuations in the potential energy δU < ε for a minimum number of timesteps tc, with integration timestep δt = 0.022 (Figure ). As the more complex structures require longer times to fully develop, the tc were increased as necessary: tc ~ 20-50 ⨉ 10 6 timesteps for one copy of the chains and simulated letters, but can reach as high as 10 8 timesteps to assemble 9 copies of the N = 10 chain.