-- find the monitor and set it as main output
local monitor = peripheral.find("monitor")
term.redirect(monitor)

local width, height = term.getSize()

local center_x = (width / 2) + 1
local center_y = (height / 2) + 1

-- base cirlce image
local circle_image = paintutils.parseImage([[
        8888888888        
    888888      888888    
  8888              8888  
  88                  88  
8888                  8888
88                      88
88                      88
88                      88
8888                  8888
  88                  88  
  8888              8888  
    888888      888888    
        8888888888        
]])
local circle_width = 26
local circle_height = 13

-- draw sweep line
local SWEEP_DELAY = 0.05
local SWEEP_AMOUNT = 18
local sweep_angle = 0

-- main loop
local quit = false

local function draw_loop()
	while not quit do
		sweep_angle = sweep_angle + SWEEP_AMOUNT

		term.setBackgroundColor(colors.black)
		term.clear()
		
		paintutils.drawImage(circle_image, center_x - (circle_width / 2) + 1, center_y - (circle_height / 2) + 1)

		local sweep_rad = math.rad(sweep_angle)
		local sweep_x = math.cos(sweep_rad) * circle_width / 2
		local sweep_y = math.sin(sweep_rad) * circle_height / 2

		paintutils.drawLine(center_x, center_y, sweep_x + center_x, sweep_y + center_y, colors.red)

		os.sleep(SWEEP_DELAY)
	end
end

local function quit_handler()
	while not quit do
		local _, key, _ = os.pullEvent("key")
		if keys.getName(key) == "q" then
			quit = true
		end
	end
end

parallel.waitForAny(draw_loop, quit_handler)

-- reset color
term.setBackgroundColor(colors.black)
term.clear()