THE 1986 Subaru Turbo XT is not a car for people who take adulthood seriously. It is a joy-toy, a hoot, a thumb of the nose at all things grown up.

I hated it at first, thought it was silly.

I was missing the point.

The Turbo XT, with its two-tone, "Mica Red-Lightning Silver" paint and its video- game instrument panel, is a celebration of much that is fun in youth. It's a four-wheeled comic strip, Buck Rogers with cylinder heads, Rambo reduced to a mock machine-gun-handle gearshift lever.

I fell in love with this car. Deeply. It's hard to explain. No matter. Walter Mitty would've understood.

Outstanding complaints: The pop-up sun roof. It's nonsense. It really doesn't let in much sun or air. The pop-up panel, when popped up, simply disfigures an otherwise smooth roofline.

A nitpick: A decorative plastic plate, designed to conceal the corner-end seams of the vinyl covering on the driver's-side door, popped out of its plastic sockets whenever the Turbo XT hit a bump.

Oh, yeah, long-legged passengers said that the car's rear seats cramped their style.

Outstanding praise: What a fun car to drive! The 1.8-liter, four-cylinder engine growls on takeoff. The instrument panel starts flashing its various digital readouts. Additional trip information, such as the number of miles the car can travel before the fuel tank runs dry, comes forth at the push of appropriate buttons.

Other cars have similar features. But Fuji Heavy Industries, maker of Subaru cars and trucks, has managed to put them together in the Turbo XT in an entertaining way. This is car as theater, and it works.

The Turbo XT's four disc brakes work well, too. Driving excitement is one thing. The ability to stop the fun, when necessary, is another. This car stops.

Acceleration, ride, handling: The Turbo XT has noteworthy small-engine performance. It increases speed without discernible body vibration. It is competent in high-speed highway traffic.

The ride is a bit hard, as befits a small sports coupe. But the experience isn't jarring. Handling is excellent.

Head-turning-quotient: A matter of great debate. Some people criticized the car's ultra- wedge front end and its upswept, yet boxy rear. They said it looked cheap and contrived. Others said it was a gutsy piece of design. The Turbo XT attracted lots of attention from both groups. I vote with the people who think that the car's body deserves commendation.

Sound system: A so-so AM/FM cassette stereo by Subaru. Hollow base tonal quality. Slightly shrill treble.

Mileage: About 27 miles to the gallon, running driver-only and with winter climate control system on most of the time. That's pretty good fuel economy for a car with this much zip. Range is also excellent, thanks to the Turbo XT's 15.9-gallon gasoline fel tank. The car is equipped with a fuel-saving, easily operated, five-speed manual gearbox.

Price-as-tested: $13,399, enough to make a man or woman out of you. But, what the heck, we've all got to grow up sometime.