fitts-lawlisted

# Fitts's Law > "The time to acquire a target is a function of the distance to and the size of the target." > — Paul Fitts, 1954 ## The core idea Fitts's Law says: the time it takes to move to and click (or tap) a target depends on two things: 1. **Distance** — how far away is the target from your starting position? 2. **Size** — how big is the target? Big targets that are close are fast and easy to hit. Small targets that are far away are slow and error-prone. This sounds obvious, but its implications for interface design are profound and frequently ignored. The mathematical form: `T = a + b * log2(2D/W)` Where T = time, D = distance to target, W = width of target. You don't need to use the formula — just internalize the ratio: **bigger and closer is always better for targets users will interact with frequently.** ## Key design implications **1. The edges and corners of screens are infinitely large (on desktop).** On a mouse-driven interface, the cursor stops at the screen edge. So a button in the corner is effectively infinitely large in two directions — you can fling your cursor toward it at full speed without overshooting. This is why the Mac menu bar is at the top of the screen, and why the Windows Start button is in a corner. Use screen edges for your most common actions. **2. Make interactive targets as large as reasonable.** Tiny click targets — small icons, thin borders, small text links — force slow, precise movements. Buttons should be large enough to hit c