An accessible alternative may swap how a task is done, never what it accomplishes

What it is

The design boundary for accessibility alternatives: substitution changes "how it's done" (input method, timing window, operation sequence) and preserves "what is accomplished" (the task's goal, the solution logic, the achievement's meaning). Goal preservation is the dividing line between accessibility alternatives and lowered difficulty—the former routes different bodies toward the same goal; the latter shrinks the goal itself. Holding this line is what earns an alternative the name "another way to play the same game" rather than "a simpler different game."

Why it happens

The goal-preservation test separates a task's goal layer from its execution layer. A task's structure: goal (open this door) → solution (find the mechanism, trigger three runes in order) → execution (input the correct sequence within the time limit). Accessibility alternatives act on the execution layer (extend the timer, simplify input, widen the window) while the goal and solution layers hold—the player still experiences the full chain of "understand the puzzle, find the method, complete the execution." The signal of crossing the line is a changed goal layer: the puzzle auto-solves (the solution skipped), the objective shifts from "defeat the boss" to "survive 60 seconds" (the goal replaced), the fight auto-plays (the play layer removed). Over-the-line substitution "helps" in the short term but changes what players receive—completing a hollowed task is not the same experience as completing the original, and long-term it places accessibility players in a second-class experience. Goal preservation also serves as the verification framework: every alternative must answer "do players using it complete the same task as standard players?"—only "yes" earns the name alternative.

Where it stops holding

Goal preservation does not mean identical execution parameters—widened windows, reduced required counts, and simplified sequences all change execution parameters. The boundary test is "the task's essential demand": a timed task's point is "decisions under pressure"; if extension keeps decision pressure (completable but requiring planning), the goal holds; if extension removes pressure (done whenever), the task has degraded. Judging the essence has subjective components, and the reliable anchor is asking "why does this task exist": a reflex QTE exists for tension (window widening keeps tension; auto-execution removes it), a memory puzzle exists for the memory challenge (no substitute should remove it). Layered alternative combinations (simplified input + original window, versus standard input + widened window) let differently limited players each approach the task's essence—more respectful of goal preservation than one universal substitute. Competitive and ranked contexts demand the strictest goal preservation (assist-configured results scored separately), while single-player allows the most freedom.

Applying it

• Write a "preservation statement" for every alternative: goal unchanged? solution layer intact? which execution parameters changed?—the statement joins design review as a required artefact.
• Share progression and achievement frameworks between alternative and standard paths (differences labelled but not segregated), so an alternative completion is a task completion.
• Verification: have two tester groups complete the same task via standard and alternative paths, comparing post-task comprehension (can they describe the solution and goal) and achievement ratings. Equivalent comprehension without significantly lower achievement passes the goal-preservation test.

Related

• Same group: W8.06.1 Time limits need extension or removal options · W8.06.2 Button mashing should be replaceable with hold or toggle · W8.06.3 Reflex checks need wider timing window options
• Nearby: J1.01 Accessibility design principles · W8.01 Difficulty options and customisation · W8.06 Timers, mashing, and reflex alternatives
• Search terms: equivalent experience · goal preservation · accessibility substitution · inclusive design