In product design, "friction" refers to any force that increases the effort required to complete an action. A form field is friction. A loading screen is friction. A confirmation dialog is friction. Each individual friction point is small. Accumulated across the user journey, they determine whether a habit forms or fails.
Habit-building apps have a specific friction problem: the habits they're trying to build need to happen at inconvenient moments. The financial logging app needs to be used at the checkout counter, when the user has the least cognitive resources to overcome friction.
The activation energy threshold
Behavioral research on habit formation identifies activation energy — the initial energy required to begin a behavior — as one of the primary determinants of habit success. James Clear's formulation: make it easy. Not merely easier — as easy as it can possibly be, because the difference between "easy" and "slightly difficult" is the difference between a habit that forms and one that doesn't.
Zero navigation. One text field. 30 seconds. The habit-building interface.
What moneytyping's interface does right
moneytyping opens directly to the text field. No home screen. No category selector. No amount field separate from the text. One thing on the screen: the cursor, blinking, waiting. The user is immediately in the action state. The 30-second timer adds urgency that reduces deliberation, which reduces the editing impulse, which produces more honest entries. Two functions. One design element. The best onboarding is the one that gets users to the core action immediately — not a tutorial, not preference screens. The action itself, as frictionlessly as possible.