CCDonut: donut.c computercraft port

-- Donut.C Ported to computercraft by nonogamer9
-- Original C Code By Andy Sloane
local A = 0
local B = 0
local z = {}
local b = {}
local screenWidth, screenHeight = term.getSize()

local function getChar(N)
    local chars = ".,-~:;=!*#$@"
    return chars:sub(math.floor(math.max(N, 1)), math.floor(math.max(N, 1)))
end

term.clear()
term.setCursorPos(1, 1)

while true do
    -- Reset buffers
    for i = 1, screenWidth * screenHeight do
        b[i] = ' '
        z[i] = 0
    end

    for j = 0, 6.28, 0.07 do
        for i = 0, 6.28, 0.02 do
            local sini = math.sin(i)
            local cosj = math.cos(j)
            local sinA = math.sin(A)
            local sinj = math.sin(j)
            local cosA = math.cos(A)
            local cosj2 = cosj + 2
            local mess = 1 / (sini * cosj2 * sinA + sinj * cosA + 5)
            local cosi = math.cos(i)
            local cosB = math.cos(B)
            local sinB = math.sin(B)
            local t = sini * cosj2 * cosA - sinj * sinA

            local x = math.floor(40 + 30 * mess * (cosi * cosj2 * cosB - t * sinB))
            local y = math.floor(12 + 15 * mess * (cosi * cosj2 * sinB + t * cosB))
            local o = x + screenWidth * y
            local N = 8 * ((sinj * sinA - sini * cosj * cosA) * cosB - sini * cosj * sinA - sinj * cosA - cosi * cosj * sinB)

            if y > 0 and y < screenHeight and x > 0 and x < screenWidth and mess > z[o] then
                z[o] = mess
                b[o] = getChar(N + 1)
            end
        end
    end

    term.setCursorPos(1, 1)
    for k = 1, screenWidth * screenHeight do
        term.write(b[k])
        if k % screenWidth == 0 then
            term.setCursorPos(1, k / screenWidth + 1)
        end
    end

    A = A + 0.08
    B = B + 0.06

    os.sleep(0.03)
end