A sequence of digits, shown once. Repeat it exactly.
TrainsImmediate recall in order: the number, the name, the instruction heard once and needed a moment later.
Sequences grow by one digit. Ends at the second miss at a length.
Train to the edge. Recover. Return.
Levels run 1 to 100. Level 100 is above Sovereign; nobody has reached it.
Infinitely scalable difficulty. It never stops getting harder.