Tapworthy

1. Touch and Go

Each screen is a big blur, only partial attention.
No depth. Users spend order of seconds using your app in sprints.
"Right tool for the right job". You perform a single, well defined task, among a user's toolbox of other apps.
No loyalty, average of 20 uses of app before abandoned or uninstalled.
Users may never understand all your app's features, gestures, or buttons.
Fat fingers. Mistakes.
You will rarely get praise for elegance. You will always get anger for inelegance.

2. Is It Tapworthy?

What does your app do, and why?
What specific problem does your app uniquely solve for users?
Elegant, precise, focused use cases. Who, what, when, where, why.
Why would you use this app when you're away from your desk or computer? Why is it especially convenient to have anytime-anywhere access to this app?
Accessory app: augments an activity.
Easy to assume the use cases are obvious when you're making it, but can only tell once consumers handle it.
Don't show/hide, enable/disable. Python zen: "Explicit is better than implicit".
Primary use cases must be painfully obvious.
Too much flashy design distracts attention, might be difficult on other platforms.
Raison d'etre:
1. "I'm Microtasking".
  - Short dashes of activity.
  - Quick, simple, sharp focus.
  - Shallow.
2. "I'm Local".
  - Sensors provide personal context.
  - GPS, motion, camera, microphone, compass.
3. "I'm Bored".
  - Distraction.
  - Exploration. Somewhere else to be. Story, escape.
Personality, uniqueness.
Think big, bold, brash in the beginning. Then "Murder your darlings" ruthlessly. Think big but build small.
Identify key activity, then how your app can help users microtask the activity in a hurry.
Subset features for most users to achieve key activities.
What is value-add over a website?
- Efficiency is a feature.
- Native polish makes content shine.
- Save it for later, offline access.

3. Tiny Touchscreen

Left-handed and right-handed one-hand access? Fat fingers? Thumb only?
Physical metaphors.
Thumbs access left/bottom or right/bottom edges, depending on handedness.
Non-idempotent actions should go in difficult areas for thumb, i.e. right/top or left/top depending on handedness.
For left-handedness, only rarely permit flipping screen controls. Usually either ignore or use full-width controls in a stack.
44px is the size of a fingertip. Practical minimum size for any tap target is 44x30 or 30x44. Actual visuals may look smaller but target should meet this.
Don't crowd the screen.
Error feedback shouldn't use audio, flash screen and maybe vibrate.
Important information at the top, controls at the bottom.
Layout loosely on a 44px grid.