He smiled for the first time in days. The exclusive library didn't just fake registers; it encoded behavior, documented errata, and offered toggles that let him explore how boot order, pull-ups, and tiny timing slips cascaded into chaos. He reworked his init sequence in the simulator: stabilise the PLL, delay peripheral clocks until the regulator trimmed, sequence the DMA only after confirming the APB flag. With the new order the simulated board glided through startup like a trained swimmer.