One-thumb controls for mobile HTML5 games in vertical feeds

Players in portrait feeds often hold the phone with one hand. If your game needs a second finger for core actions, you are silently cutting your audience. One-thumb design is not dumbing down—it is respecting physics.

Map the primary action to the lower third

Thumbs reach the lower screen more reliably than top corners. Put jump, shoot, or steer where the thumb naturally rests. Avoid tiny hit targets; 44px is a good minimum for casual games. Test on real devices, not only desktop emulators.

Reduce mode switches

Every time the player changes grip, you risk a drop. If you need secondary actions, use short holds, double taps, or contextual buttons that appear near the thumb path—not opposite corners. Pair with Portrait feed attention economics for AI mini games.

Prompt agents explicitly

When using text-to-game flows, include “one-thumb portrait controls” in the prompt alongside loop description. See Text-to-game prompt patterns that actually ship for templates.

Compare platforms on mobile defaults

Some AI stacks default to keyboard-first demos. Ask whether the product tests on mobile web by default. Compare with Astrocade includes mobile and publishing angles in its question set.