span_controller

local controller = peripheral.wrap("right")
local g_level = controller.getTargetSpeed()
local statelist = {
    ["top"] = redstone.getInput("top"),
    ["left"] = redstone.getInput("left"),
}
local function init()

end

local function set_speed(pLevel)
    g_level = g_level + pLevel
    if g_level > 256 then
        g_level =256
    elseif g_level < -256 then
        g_level = -256
    end
    -- print(g_level)
    controller.setTargetSpeed(g_level)
end

local function redstoneCheck()
    while true do
        os.pullEvent("redstone")
        for side, state in pairs(statelist) do
            if redstone.getInput(side) ~= false then
                if side == "top" then
                    set_speed(4)
                elseif side == "left" then
                    set_speed(-4)
                end
                break
            end
        end
    end
end

-- parallel.waitForAny(redstoneCheck)
redstoneCheck()