Write the loop as verbs
Use a short chain such as “spot a gap, tap to jump, land or fall, try again.” If the chain contains several “and then” clauses, identify which action is essential and postpone the rest. In Stack, for example, the visible cycle is a moving slab, a tap, a trimmed or centered landing, then a changed target. That example describes the player-facing loop, not the catalogue game’s source code.
Make the consequence visible
Every action in a useful prototype should produce feedback that helps the player understand the result. Show whether the jump cleared the gap, whether a shot hit, or whether a choice changed the board. If testers cannot tell what their input did, add a clearer response before adding more content. Keep the first version narrow enough to adjust one variable, such as gap width, and play again immediately.
Test repetition, not just first contact
Let someone try several loops without explaining each step. Ask what they expected, where they hesitated and what made them continue or stop. Watch for repeated confusion, but do not treat one person’s preference as universal. Compare the intended rule with what the screen communicates. MDN describes a game cycle as presenting a situation, receiving input, interpreting it and calculating a new situation; use that as a practical checklist for the prototype’s turn or frame.
Questions about prototype a game core loop
How much of a game should a prototype contain?
Only enough to test the design question. A working action, consequence and repeat opportunity are often more useful than unfinished menus or many levels.
When is the core loop ready to expand?
Expand when players can understand the action, see its result and make another choice for reasons your design intended. Then test whether added content preserves that loop.