This document provides insights from Matt Rix, creator of the puzzle game Trainyard, on his approach to level design. He views level design as teaching players new skills and concepts gradually over time. Some key points include introducing new elements one at a time, treating combinations of elements as new, providing visual instructions rather than text, ensuring players practice all taught skills, and considering different player types when designing difficulty and unlocking levels. The goal is to create a smooth learning curve that avoids frustrating players.