function love.load()
	--options
	love.graphics.setColor(1,1,1)
	love.graphics.setDefaultFilter("nearest") -- good pixel

  SCREEN_WIDTH = love.graphics.getWidth()
  SCREEN_HEIGHT = love.graphics.getHeight()

  -- simulation variables
  CONST_G = 39.5
  CONST_S = 0.15

  T = 0
  DT = 1/120
  TIME_SPEED = 0.25

  VIEW = {}
  VIEW.x = 0
  VIEW.y = 0
  VIEW.prints = {}

  require "class"
	require "body"

	newBody(
	  {0, 0, 0},
	  {0, 0, 0},
	  40000,
	  {1,0,0}
	)
	newBody(
	  {10000, 0, 0},
	  {0, 100000, 0},
	  200,
	  {0,1,0}
	)
	newBody(
	  {20000, 0, 0},
	  {0, 100000, 0},
	  400,
	  {0,0,1}
	)
	newBody(
	  {0, 20000, 0},
	  {-200000, 0, 0},
	 3000,
	  {0,1,1}
	)
end

function love.update(dt)
  T = math.floor((T + DT * TIME_SPEED)*1000)/1000
  UpdateBodiesAcceleration()
  UpdateBodiesVelocity(DT * TIME_SPEED)
  UpdateBodiesPosition(DT * TIME_SPEED)
end

function love.draw()
  -- center camera on bigger one
  local vm = 0
  for n, body in pairs(BodyList) do
    if body.mass > vm then
      vm = body.mass
      VIEW.x = -body.x
      VIEW.y = -body.y
    end
  end
  local vm = 0
  for n, body in pairs(BodyList) do
    if body.max_distance > vm then
      vm = body.max_distance
      VIEW.size = math.sqrt(body.max_distance)
    end
  end

  love.graphics.setColor(1,1,1)
  -- draw bodies
  for n, body in pairs(BodyList) do
    addPrint(body)
  end
  drawPrints()
  -- draw info
  love.graphics.setColor(1,1,1)
  love.graphics.print("x,y: " .. VIEW.x .. VIEW.y .. " size: " ..  VIEW.size .. " T: ".. T)
  for n, body in pairs(BodyList) do
    love.graphics.setColor(body.color[1],body.color[2],body.color[3])
    love.graphics.print("mass: "..body.mass..", x,y: "..body.x..", "..body.y..", vx, vy:"..body.vx..", "..body.vy,0,15*n)
  end
end

function addPrint(body)
  VIEW.print_time = 10
  table.insert(VIEW.prints,{
    pos = {
      x = body.x,
      y = body.y
    },
    mass = body.mass,
    color = body.color,
    time = VIEW.print_time
  })
end

function drawPrints()
  for n, print in pairs(VIEW.prints) do
    love.graphics.setColor(print.color[1],print.color[2],print.color[3],print.time/VIEW.print_time)
    love.graphics.circle("line",(VIEW.x+print.pos.x)/VIEW.size+SCREEN_WIDTH/2,(VIEW.y+print.pos.y)/VIEW.size+SCREEN_HEIGHT/2,(print.time/VIEW.print_time)*math.sqrt(print.mass)*5/VIEW.size)
    print.time = print.time - 1
    if print.time < 1 then VIEW.prints[n] = nil end
  end
end