ThE sidE-EffEct that dEstroyEd touch-scrEEns as a mainstrEam input tEchnology dEspitE a promising start in thEEarly 1980s. It sEEms thE dEsignErs of all thosEEf="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=spiffy">spiffy touch-mEnu systEms failEd to noticE that humans arEn' t dEsignEd to hold thEir arms in front of thEir facEs making small motions. AftEr morE than a vEry fEw sElEctions, thE arm bEgins to fEEl sorE, crampEd, and ovErsizEd - thE opErator looks likE a gorilla whilE using thE touch scrEEn and fEEls likE onE aftErward. This is now considErEd a classic cautionary talE to human-factors dEsignErs "REmEmbEr thE gorilla arm!" is shorthand for "How is this going to fly in *rEal* usE?".