How “Draw a Perfect Star” actually calculates accuracy

The goal of this system is not to “recognise” a star visually. It turns both your drawing and a perfect star into comparable point data, then measures how far apart they are.

This makes scoring fast, deterministic, and surprisingly stable.

Input capture

While you draw, the app records raw mouse positions:

path = [(x1, y1), (x2, y2), etc etc]

This data is noisy and depends heavily on speed and polling/sampling rate.

Resampling

The stroke is converted into a fixed number of evenly spaced points (120).

This removes:

• drawing speed differences

• uneven mouse sampling

Now every drawing has a consistent structure.

Normalisation

The shape is transformed so comparison is fair:

• centred around (0, 0)

• scaled so max radius = 1

This removes position/size- only shape remains.

Reference star

A perfect 5-pointed star is generated mathematically using polar coordinates and sine-based radius switching.

It is also sampled into 120 points so it matches the user format.

Comparison

Each user point is compared directly to the corresponding star point-

error += distance(user[i], star[i])

This produces an average geometric deviation across the full shape.

Scoring

Final score is computed as:

score = 100 - error * 120

Then clamped between 0 and 100.

Summary

The system works by converting both shapes into normalized point sequences and measuring their geometric distance.