level_color = {0.8,0.8,0.8}

  color(0.8,0.8,0.8)

  color(unpack(level_color))

  -- level navigation
  local ns, ps = tostring(curr_level+1), tostring(curr_level-1)
  local nw, pw = App.width(ns)+10, App.width(ps)+10
  local h = Line_height+10
  local nx,px, y
  if Safe_width > Safe_height then
    px, nx = left-side-pw-10, left+lw*side+side+10
    y = top + lh*side/2
  else
    px, nx = left+side+10, left+lw*side-side-nw-10
    y = top-side-h-10
  end
  if curr_level > 1 then
    button(ui_state, 'previous level', {x=px, y=y, w=pw, h=h,
      bg=bg, onpress1=previous_level,
      icon=function(p)
        color(unpack(level_color))
        g.print(ps, p.x+5, p.y+5)
      end,
    })
  end
  if curr_level < #levels then
    button(ui_state, 'next level', {x=nx, y=y, w=nw, h=h,
      bg=bg, onpress1=next_level,
      icon=function(p)
        color(unpack(level_color))
        g.print(ns, p.x+5, p.y+5)
      end,
    })
  end

    if curr_level < #levels then
      curr_level = curr_level+1
      level_state = load_level(levels[curr_level])
    end

    next_level()

    if curr_level > 1 then
      curr_level = curr_level-1
      level_state = load_level(levels[curr_level])
    end

    previous_level()

function next_level()
  if curr_level >= #levels then return end
  curr_level = curr_level+1
  level_state = load_level(levels[curr_level])
end
function previous_level()
  if curr_level <= 1 then return end
  curr_level = curr_level-1
  level_state = load_level(levels[curr_level])
end