I giggled my way through Starship Troopers, and at the end I still wasn't sure exactly what I had been laughing at. It's a broad spoof of war propaganda - an exercise in gung-ho-ho.

It would be incorrect to say that the film works on many different levels, since it rarely works at all, though you might say that it is open to a baffling number of different interpretations. It appears both to celebrate and satirise the blond-haired, blue-eyed space cadets who are dispatched from their futuristic fascist homeland to battle the Bugs, giant killer arachnids bent on universal domination.

The director, Paul Verhoeven, devotes much of the film to these cadets and their boring, competitive, Beverly Hills 90210 lives, ticking off a checklist of the components of teenage soap opera: the love triangles, the parental conflict, even the bland colours and prosaic camerawork. You don't care when most of the characters get sliced to ribbons in the second half, and Verhoeven doesn't want you to - it's just a big, perverse joke. You go with it or you don't. And even if you do, it can still leave you feeling lousy, like the worst sitcoms or fast food.

There are no punchlines, though the violence has a brutal comic kick, and there is some self-consciously awful dialogue that recalls the film's influences - Them and The Blob, and the recent Tremors. The funniest sections are the television broadcasts advising citizens on how they can do their bit for the war effort, though these are basically the same routines that spiced up Verhoeven's earlier film Robocop. Starship Troopers can be very unsparing in its satire, but what it lacks is any purpose; it gets so that all you're laughing at is the film's knowingness - there's nothing behind its mean-spirited pose.

Here and there, you can detect Verhoeven's subversive tendencies jostling for space. His wittiest film, The Fourth Man, is echoed when the handsome, shirtless young hero gets a public lashing and Verhoeven wrings out every last sweaty drop of homo-eroticism from the scene. And the Bugs themselves are agreeably nasty, lungeing and jabbing with their scissor-blade limbs, swarming over the horizon like a platoon of Swiss army knives. The battle scenes provide flashes of pure, vicious slapstick - when a Bug swallows a grenade, there's even a cartoon gulping noise on the soundtrack before the creature erupts, covering innocent bystanders in a snot-and-bolognese chowder. It's like hard-core pornography for Rentokil men.

If you're looking for something soothing after Starship Troopers, don't turn for comfort to the re-release of Douglas Sirk's intoxicating 1956 melodrama Written on the Wind. Although the film is a lush, over-ripe little masterpiece, it remains something of a relief that they don't make 'em like this any more - if they did, we would all be on the verge of a nervous breakdown.

Robert Stack plays the reckless, impotent son of an oil tycoon, with Lauren Bacall as his long-suffering wife, Dorothy Malone as the kid sister who seeks solace in any old arms, and Rock Hudson as Stack's best pal, all of them caught up in a violent emotional tornado. It's a film to convince you of two things: Douglas Sirk was a genius; and there's always somebody worse off than you.

`Starship Troopers' (cert 15) is on general release from today. `Written on the Wind' (PG) is at the Everyman, Hampstead, and Curzon Phoenix from today, and at the NFT from 9 January.