What is different from developing for phone

No touch screen

• User interface is either touch slider, line of sight, camera, voice or else

Head up display

The display and on-screen objects behave differently

• The background is transparent (black). Try the glasses on, you will see what We're talking about
• The size of the objects projected are different from their pixel sizes
• The relevant display area is some-what elliptic even though the physical is rectangular

Its not a smartphone

No screen, no keyboard, (almost) No buttons

HUD UI is required

No basic smartphone elements, e.g. lack of notifications bar