function dump(o)
   if type(o) == 'table' then
      local s = '{ '
      for k,v in pairs(o) do
         if type(k) ~= 'number' then k = '"'..k..'"' end
         s = s .. '['..k..'] = ' .. dump(v) .. ','
      end
      return s .. '} '
   else
      return tostring(o)
   end
end

TICK_DELAY = 1 / 25

shapes = { }
function init_shapes()
    if shapes.img ~= nil then hide_image(shapes.img) end
    if shapes.cursor ~= nil then hide_image(shapes.cursor) end

    shapes.cursor = color_surface(8, 8, 0, 0, 0)
    shapes.img = fill_surface(VRESW, VRESH, 0xff, 0x77, 0x00) 

    show_image(shapes.img)
    show_image(shapes.cursor)
end

function exercise1()
    print("Hello World!")
    warning("Hello Warning!")

    init_shapes()
    
    cursor_setstorage(WORLDID)
end


function exercise1_input(evtbl)
    if evtbl.source ~= "mouse" then return end
    if evtbl.samples == nil then return end
    x, y = cursor_position()
    sample = evtbl.samples[1]
    if evtbl.subid == 0 then
        move_cursor(sample, y)
    elseif evtbl.subid == 1 then
        move_cursor(x, sample)
    else
        warning("Unknown subid " .. evtbl.subid)
    end

end

function exercise1_input_end()
    x, y = cursor_position()
    move_image(shapes.cursor, x, y, TICK_DELAY)
    warning("Mouse: " .. x .. ", " .. y)
end

function exercise1_display_state(action, id, state)
    warning("Res: " .. VRESW .. ", " .. VRESH)
    init_shapes()
end