var posx, posy, y1, y2, radius, drawx, clr : real
var thickness : int
% two y values (y1 and y2) are necessary because at each x coordinate, there is a top and bottom y coordinate
radius := 50
posx := 100 % x position of centre of cirlce
posy := 100 % y position of centre of cirlce
clr := 31 % colour of cirlce
thickness := 2 % thickness of cirlce in pixels

setscreen ("graphics:200;200, nobuttonbar, title:Circle Draw")
colourback (black)
cls

% calculates y values for each x coordinate
function Y (x, radius : real) : real
    if radius ** 2 - x ** 2 > 0 then
        result sqrt (radius ** 2 - x ** 2)
    else
        result - sqrt (- (radius ** 2 - x ** 2)) % avoids 'negative value passed to Sqrt' error
    end if
end Y

for count : 0 .. thickness - 1
    clr_draw := clr
    drawx := count % shifts next layer over a pixel to create a thick outline
    loop
        drawx += .001
        if clr_draw > 0 and clr_draw < 255 then
            clr_draw -= .0001
        end if
        y1 := Y (drawx - radius, radius - count) + posy % calculates UPPER y coordinate
        y2 := -Y (drawx - radius, radius - count) + posy % calculates LOWER y coordinate
        drawdot (round (drawx + posx - radius), round (y1), round (clr_draw)) % draws UPPER y coordinate
        drawdot (round (drawx + posx - radius), round (y2), round (clr_draw)) % draws LOWER y coordinate
        exit when drawx >= 2 * radius - count
    end loop
end for

for i : 0..359
    drawdot (round (10* cos (i)) +50,round (10* sin (i))+50, 24 + round (7* sin (i)))
end for