A checkbox that was never broken
01 // OBSERVED SYMPTOM
Platform selection in the post composer did nothing when clicked.
02 // ROOT CAUSE DIAGNOSIS
The checkbox toggled correctly the entire time and the selection was genuinely recorded. The selected styling was losing a CSS specificity tie: both class sets were single-class selectors, so source order in the compiled stylesheet decided the winner. The confirmation tick did un-hide on every click, but it renders white on a square that stayed white.
03 // ARCHITECTURAL FIX
Three earlier theories were tested and discarded before the markup was reproduced against the production stylesheet in a real browser and the computed styles measured. The fix removes the unselected classes on toggle instead of layering the selected ones on top. No stylesheet rebuild required.






