turrent

local event
local degree = 0

local deltaDeg = math.pi/20
local minDeg = -0.3*math.pi
local maxDeg = 0.3*math.pi

local function shot()
  while true do
    local tag = string.format("{Motion:[0:%fd,1:%fd,2:%fd]}",math.sin(degree)+0.001,0.2,math.cos(degree)+0.001)
    commands.summon("Arrow","~","~1","~",tag)
    if (minDeg and degree + deltaDeg < minDeg) or (maxDeg and degree + deltaDeg > maxDeg) then
      deltaDeg = -deltaDeg
    end
    sleep(0.1)
    degree = degree + deltaDeg
  end
end

local function stop()
  os.pullEvent("char")
end

parallel.waitForAny(shot,stop)