local zoom = 0

local function zoomIn()
    mp.command("add video-zoom 0.05")
    zoom = mp.get_property_number("video-zoom", 0)
    mp.osd_message(string.format("Zoom: %.2f", zoom))
end

local function zoomOut()
    mp.command("add video-zoom -0.05")
    zoom = mp.get_property_number("video-zoom", 0)
    mp.osd_message(string.format("Zoom: %.2f", zoom))
end

local function zoomReset()
    mp.command("set video-zoom 0")
    mp.osd_message("Zoom reset")
end

mp.add_forced_key_binding("+", "zoomIn", zoomIn)
mp.add_forced_key_binding("-", "zoomOut", zoomOut)
mp.add_forced_key_binding("0", "zoomReset", zoomReset)