Yídàn zhīdao le jiéjú, zhège yóuxì jiù biàn de suǒrán-wúwèi le.
Once you know the ending, the game becomes completely boring.
Tips
usage
Mostly said of writing, films and talks, and of a pastime that has lost its charm. 枯燥无味 "dry and dull" is close; 津津有味 "with great relish" is the opposite.
