do all undercover cops like rooftops?

That's Andy Lau's Inspector Lau, a triad mole in the police force confronting Tony Leung Chiu Wai's Yan, an undercover cop, as they face off on the roof in Infernal Affairs (imdb page), a high-profile technology-heavy Hong Kong cop flick that's worth every minute of it. Slick, fast-paced, grittily-filmed, well-acted, and accompanied by a background score that bore two little appealing motifs (the first: an arabian riff; the second: a Herrmann-esque riff arranged for cello, violin, electric guitar and drum). The bookending Buddhist quotes don't make too much sense. The female roles are underwritten, and ineffectual. But the morse code idea and the complex double switcheroo (an undercover cop having trouble getting out of being a mole/a triad mole in the police department dealing with conflicting goals and a growing conscience) are worth the watch. The only true downside is that they chose to use white as the colour for the subtitles (and even placed them within the film instead of in the black bars -- although widescreen TVs would miss on the latter, come to think of it!), and this sucks against the texture of the film (lots of whites, trust me). Nevertheless, be patient and you will be rewarded. (see also: Chhal)