minetest.register_on_joinplayer(function(player)
player:set_hp(20)
player:set_attribute("a:hp",100)
end)

minetest.register_on_player_hpchange(function(player, hp_change)

if hp_change < 0 then
local gethp = tonumber(player:get_attribute("a:hp"))
local newhp = gethp + hp_change
minetest.chat_send_all(newhp)
player:set_attribute("a:hp",newhp)

if newhp <= 0 then
player:set_attribute("a:hp",100)
return -20
end

end

if hp_change ~= 20 then
return 0
else
return 20
end

end, true)