Drawing a circle is actually pretty simple! Say we want to draw one with:

• radius r=5
• center C=(0,0)
• 1000 points

The logic would be:

for (let i = 0; i < 1000; i++) {
    // full circle is made up of 2 * PI angles -> calculate current loop angle
    const angle = (2 * Math.PI) * (i / 1000)
    const x = r * Math.cos(angle)
    const y = r * Math.sin(angle)
    drawPixel(x, y)
}

The circle starts being drawn at (5, 0). As y approaches -5, x gets smaller until it hits 0. Then x approaches -5 and y approaches 0, and so on.