Notes on designing controls for a thumb, not a mouse
Porting a desktop game to mobile is not a layout change. It is a redesign of every input the player makes.
The single biggest mistake in browser game development is treating the mobile version as a resized desktop version. It is not. A thumb covers a substantial part of a phone screen, has no hover state, and cannot be precise to a single pixel while also being fast.
The most common fix we make is to delete precision requirements. If a desktop mechanic asks the player to click a two-pixel target, the mobile version either widens the target or replaces the click with a swipe in a generous direction. Precision without tolerance is a desktop luxury.
The second fix is to move the interaction away from the bottom of the screen, where the hand sits. Any control that a player has to reach under their own thumb is a control that will be pressed by accident.
The third fix is latency honesty. Touch input arrives in bursts and a game that reads every event as a deliberate action feels twitchy and unfair. Adding a few milliseconds of smoothing makes a thumb game feel far more precise than it is, and players describe this as “responsive” even though it is technically the opposite.
None of this is visible in the final product and all of it is the difference between a game you tap once and a game you keep open.