Solutions guide
Solved netlists for all 10 levels. Each board shows the legal routing — study the layer jumps, the meanders, and where the via drops happen to keep timing matched.
Layer rule
Metal 1 · cyan (solid)
Metal 2 · magenta (dashed)
M2 is only used when traces would otherwise cross on the same layer (drop a via to tunnel under), or when an obstacle blocks M1 entirely. Otherwise M1 alone is the cleanest answer.