Formula 17 (17歲的天空, pinyin: shí qī suì de tiān kōng) is a 2004 film which was directed by Chen Yin-jung (陳映蓉). It stars Tony Yang (楊佑寧), Duncan (周群達), King Chin (金勤), Dada Ji (季宏全), Jimmy Yang (楊俊明), and Jason Chang (張大鏞). It is a gay romantic comedy film about Chou T'ien-Tsai, a romantic Taiwanese male who takes a trip to visit an online boyfriend in person for the first time. Finding his internet relationship unsuitable for his real life, he moves on with his life and rooms with an old time friend of his. The film describes T'ien's experiences with his loyal roommate and his friends, and a surprising relationship that he develops with the local "Playboy".

This film was banned in Singapore because it "portrayed homosexuality as normal, and a natural progression of society"

Directed by Chen Yin-jung
Produced by Aileen Li
Written by Rady Fu
Starring Tony Yang & Duncan Lai
Distributed by Strand Releasing
Release date(s) 2 April 2004 (Taiwan)
Running time 93 min.
Language Mandarin, Cantonese

Plot summary

Naive countryman Chou T'ien-Tsai goes to Taipei to meet an internet friend face-to-face. Being a romantic, and believing in 'true love' (he even has a book called Love Is A Kind Of Faith), he is sorely disappointed when his friend suggests they have sex with no love. T'ien instead goes to a bar and runs into his ex-classmate Yu and in the process meets the 'Number One Playboy' Bai Tie Nan, who is notorious for one night stands. T'ien very quickly develops a liking towards Bai.

After the night at the bar and becoming roommates with Yu, T'ien gets a job as a pool attendant and has several run-ins with Bai, who seems to like T'ien mutually. Scenes with Bai and his psychologist show that Bai has a problem kissing people. After being advised to practice kissing a mirror and then a dummy, both of which fail to help him, he tries to kiss his longtime friend, but can't bring himself to do it.

One night, T'ien shows up at Bai's doorstep and they end up having sex consensually. True to his nature, Bai disappears the next day, leaving his friend to turn up at his house and explain to T-ien that 'he hopes you don't misunderstand'. T'ien, hurt and unknowing of the entire story behind Bai's intimacy issues, leaves a message saying that 'this kind of misunderstanding won't happen again'.

T'ien prepares to leave his roommate's dwelling and return to his own home. In the meantime, T'ien's friends corner Bai. They asked Bai to tell them the truth Bai is very resistant to tell the story, so his best friend decides to share instead. As a young boy, Bai was told by a fortune teller that he is cursed and that anything that he loves will be doomed. A lifetime of self-fulfilling this prophecy is what led Bai to become a serial one-night stander and lose his ability to love. Falling in love with T'ien caught Bai off guard and, as a result, they both suffered. After a silent prayer for a second chance, he sees T'ien heading up an escalator. His first attempt to apologize fails, and T'ien literally runs away. He nearly gets run down by a scooter, but Bai saves him and they make up.

The ending credits include a short segment on the three supporting cast members and their somewhat stereotyped views upon gay fashion.