function build_gui(player)
    -- here only build gui, but not try to update it with player data that is not always already available (in init_player for example)
    local guif = player.gui.top.flw_zoom

    if guif == nil then
        guif = player.gui.top.add({type = "flow", name = "flw_zoom", direction = "horizontal", style = "zoom_flow_style"})
        guif.add({type = "sprite-button", name = "but_zoom_zout", sprite = "sprite_zout", style = "zoom_sprite_style"})
        guif.add({type = "sprite-button", name = "but_zoom_zin", sprite = "sprite_zin", style = "zoom_sprite_style"})
    end
end



local function on_gui_click(event)
    local player = game.players[event.player_index]

    if event.element.name == "but_zoom_zin" then
        player.zoom = player.zoom*player.mod_settings["some-zoom-zoomchangefactor"].value

    elseif event.element.name == "but_zoom_zout" then
        player.zoom = player.zoom/player.mod_settings["some-zoom-zoomchangefactor"].value

    end
end



local function on_runtime_mod_setting_changed(event)
    local player = game.players[event.player_index]
    if player.connected then
        player.zoom_limits = {}
        local defzoomlimit = player.zoom_limits
        local zoomlimitfactor = 1

        player.zoom_limits = {
            furthest = { distance = defzoomlimit.furthest.distance*player.mod_settings["some-zoom-zoomlimitfactor"].value, max_distance = defzoomlimit.furthest.max_distance*player.mod_settings["some-zoom-zoomlimitfactor"].value},
            furthest_game_view = { distance = defzoomlimit.furthest.distance*player.mod_settings["some-zoom-zoomlimitfactor"].value, max_distance = defzoomlimit.furthest.max_distance*player.mod_settings["some-zoom-zoomlimitfactor"].value}
        }
    end
end



local function on_init()
    for _, player in pairs(game.players) do
        if player.connected then
            player.zoom_limits = {}
            local defzoomlimit = player.zoom_limits
            local zoomlimitfactor = 1

            player.zoom_limits = {
                furthest = { distance = defzoomlimit.furthest.distance*player.mod_settings["some-zoom-zoomlimitfactor"].value, max_distance = defzoomlimit.furthest.max_distance*player.mod_settings["some-zoom-zoomlimitfactor"].value},
                furthest_game_view = { distance = defzoomlimit.furthest.distance*player.mod_settings["some-zoom-zoomlimitfactor"].value, max_distance = defzoomlimit.furthest.max_distance*player.mod_settings["some-zoom-zoomlimitfactor"].value}
            }
            build_gui(player)
        end
    end
end


script.on_event(defines.events.on_runtime_mod_setting_changed, on_runtime_mod_setting_changed)
script.on_event(defines.events.on_gui_click, on_gui_click)
script.on_init(on_init)