function blockgame.get_keys (tab)
	local keyset = {}
	local n = 0
	for key, value in pairs(tab) do
		n = n + 1
		keyset[n] = key
	end
	return keyset
end

function blockgame.shallow_copy_table (tab)
	local result = {}
	for key, value in pairs(tab) do
		result[key] = value
	end
	return result
end