That's how me and my brother learned to program graphics and games as 14-year olds. We disassembled over 50% of Manic Miner on the Sinclair Spectrum using an hex-to-opcode sheet, lots of pen and paper, and oh yes tracing lines along the jumps. Fun times! (I continued ripping apart many other Spectrum games, but with actual disassemblers)

All it required was: free time, motivation and, above all, a mind free of assumptions and structure, ready to learn and be filled no matter the effort.