function setpixel(table, n, x, y)
    local tx = math.floor(n/2)+x
    local ty = math.floor(n/2)+y

    table[ty+1][tx+1] = 'x'
end

function init(pixels, radius)

    intRadius = math.floor(radius)
    n = 2*(intRadius+1) + 1

    -- go up and move past the circle
    turtle.up()
    for i=1,intRadius+1 do
        turtle.forward()
    end
    turtle.turnLeft()

    -- set empty spaces to dot
    for y=1,n do
        pixels[y] = {}
        for x=1,n do
            pixels[y][x] = '.'
        end
    end

    -- fill in circle pixels
    local l = math.floor(radius * math.cos(math.pi/4))

    for x=0,l do
        y = math.floor(math.sqrt(radius*radius - x*x))
        setpixel(x, y)
        setpixel(-x, y)
        setpixel(x, -y)
        setpixel(-x, -y)
        setpixel(y, x)
        setpixel(-y, x)
        setpixel(y, -x)
        setpixel(-y, -x)
    end

end

function printGrid(table)
    for y=1,#table do
        for x=1,#table do
            write(table[y][x])
        end
        print()
    end
end

print(turtle.refuel())
os.loadAPI("lib.lua")

local maxy = 1
local radius = 3
local intRadius = math.floor(radius)
local pixels = {}
init(pixels, radius)

local posx, posy = intRadius+2, n
local vx, vy = -1, 0

function pixelLeft(posx, posy, vx, vy)
    vvx, vvy = left(vx, vy)
    xx, yy = posx+vvx, posy+vvy
    print('checking left: ', xx, yy)
    if (xx < 1) or (xx >= n) then
        return false
    end
    if (yy < 1) or (yy >= n) then
        return false
    end
    return pixels[yy][xx] == 'x'
end

function pixelForward(posx, posy, vx, vy)
    xx, yy = posx+vx, posy+vy
    if (xx < 1) or (xx >= n) then
        return false
    end
    if (yy < 1) or (yy >= n) then
        return false
    end
    return pixels[yy][xx] == 'x'
end

function moveAndPlace(posx, posy, vx, vy)
    posx, posy = posx+vx, posy+vy
    turtle.forward()
    if lib.currentSlotEmpty() then
        lib.reSelect()
    end
    turtle.placeDown()
    return posx, posy
end

function mainLoop(posx, posy, vx, vy)
    print(posx, posy)
    if pixelLeft(posx, posy, vx, vy) then
        print('pixel left!')
        if pixelForward(posx, posy, vx, vy) then
            print('pixel forward!')
            vx, vy = lib.turnRight(vx, vy)
        end
    else
        vx, vy = lib.turnLeft()
    end
    posx, posy = moveAndPlace(posx, posy, vx, vy)
end

local currenty = 0
repeat
    -- one circle in xz plane
    repeat
        mainLoop(posx, posy, vx, vy)
    until (posx==intRadius+2) and (posy==n)
    currenty = currenty+1
    turtle.up()
    print('one more layer finished!')
until currenty==maxy
print('done! :)')