You can indicate that an error occurred using haptic feedback. It can be useful for long-running tasks that fail, like page loads or downloads. But you can also use it as errors occur like Twitter does when reaching the character limit.
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A reminder that the more modes we use to convey important information, the more sure we'll be that it will be perceived by all our users. Consider a combination. of color, icons, messages, sound, haptics, animations, etc.
If, for some reason, you are creating a button from scratch, instead of relying on UIButton (perhaps you are adding a fancy micro interaction animation?), take into account that you’ll need to configure the button accessibility trait.
Images can automatically scale for accessibility content size categories, by setting the adjustsImageSizeForAccessibilityContentSizeCategory property to true, for any UIImageView you'd like to get its size adjusted. https://developer.apple.com/documentation/uikit/uiaccessibilitycontentsizecategoryimageadjusting/adjustsimagesizeforaccessibilitycontentsizecategory
