p={}
p.platforms={}
function p:new(x,y,w,h)
    platform={}
    platform.x=x
    platform.y=y
    platform.w=w
    platform.h=h
    table.insert(p.platforms, platform)
end
function p:clear()
  for k in pairs (p.platforms) do
    p.platforms[k] = nil
  end
end