3.1。f非精神图标................................................................................................................................................................................................................................. 9 3.2。C ONTEXTUAL ICONS ............................................................................................. 9 3.3.i Con s tyles ......................................................................................................................................................................................................................................................................................................................................................................................................................................... 10 3.4。I CON SIZES ....................................................................................................... 10 3.5.I CON OPTIONS ................................................................................................... 11 3.6.c rowdesourcing库...............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................M ANDATORY CHECKLIST ...................................................................................... 12 3.8.B EST PRACTICES & RECOMMENDATIONS .................................................................. 13