Thumb Zone

The area of a touchscreen naturally reachable by the thumb during one-handed play, a physical constraint that should define the placement of all primary interactive elements.

In games, this means

On a modern large-screen phone, the top third of the screen is essentially unreachable with one thumb. Placing critical actions, attack buttons, primary navigation, emergency exits, outside the thumb zone forces awkward grip shifts that break flow and cause mis-taps. Every mobile game UI should be thumb-zone mapped before finalising layout.