local timer = 0

minetest.register_globalstep(function(dtime)

	timer = timer + dtime

	-- every 1 second
	if timer < 1 then
		return
	end

	-- reset time for next check
	timer = 0

	-- loop through all players
	for _,player in ipairs(minetest.get_connected_players()) do

		-- get player position and add 1.5 for head level
		local pos = player:get_pos() ; pos.y = pos.y + 1.5

		local health = player:get_hp()

		if health > 0 then

			-- show particle
			minetest.add_particle({
				pos = pos,
				velocity = {
					x = math.random() - 0.5,
					y = math.random(0.4, 1.0),
					z = math.random() - 0.5,
				},
				size = math.random(2, 4),
				vertical = true,
				texture = "heart.png",
			})
		end
	end
end)