Reduced precision.
WHO THIS AFFECTS
People with tremor, limited dexterity or pain People using one hand Anyone on a moving vehicle
WHAT TO DO
Make targets large Space them apart Avoid requiring precision Avoid time limits
WHAT SIZE TARGETS
Large enough to hit reliably with a thumb.
Small targets are a constant source of error.
WHAT SPACING
Enough that a near miss does not trigger something else.
Particularly where one action is destructive.
WHAT TO AVOID
Actions requiring dragging, without an alternative Actions requiring a precise hover Double actions Anything requiring sustained pressing
WHAT TO PROVIDE
An alternative to any gesture Undo, rather than confirmation, where possible
WHY UNDO
It is less work than confirming every action, and it recovers genuine mistakes.
WHAT TO AVOID IMPOSING
Timeouts that discard work.
WHAT TO DO IF A TIMEOUT IS NECESSARY
Warn before it expires and allow extension.
WHAT TO TEST
Operating the interface one-handed on a phone.
