A useful distinction
A core gameplay loop is the recurring action-and-feedback pattern a player experiences. In a tile puzzle, selecting a tile, changing the arrangement and evaluating the new state may form that pattern. A narrative introduction is a different part of the design.
Put it into practice
Draw three boxes describing the repeated sequence in your own prototype. Identify which step asks for a decision and which explains the consequence. Keep the example small enough that you can test it without a long tutorial or a complete fictional world.