📐 Science

What is Fitts' Law and how does it apply to aiming?

Fitts' Law, formulated by Paul Fitts in 1954, is the fundamental model of human pointing movement. It states that the time to reach a target is a function of the distance to the target divided by the width of the target. The further away or smaller the target, the longer it takes to click accurately.

Movement time = a + b × log₂(2D / W)
Where D = distance to target centre, W = target width, a/b = empirical constants
The log₂ term is the "index of difficulty" — it quantifies how hard a target acquisition is

In gaming terms: a small enemy head at long range has a high index of difficulty; a large, close target is easy. The Aim Trainer test is directly grounded in Fitts' Law — target size and spacing follow the model so your score reflects your personal speed-accuracy tradeoff point on the Fitts curve.

Practical implication: Aim training at the same target size every session will plateau you. The best aim trainers progressively shrink target size and increase distance — continuously pushing your index of difficulty higher.

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