HONG KONG (Reuters Life!) - As a youngster living in a tiny flat with six others in one of the world's most densely populated cities, Hong Kong architect Gary Chang has been obsessed by living space, or rather a chronic lack of it.

After three decades in the same boxy, 32-square-meter (344 sq ft) dwelling he grew up in, Chang has come up with an innovative answer to the increasingly cramped lives of many urban dwellers -- the science fiction-like "domestic transformer."

"The idea is everything is moving. This is my laundry space," Chang told Reuters, sliding away a wall filled with CDs to reveal a washing machine and dryer.

By sliding another track-mounted metal wall that bears a plasma TV, a kitchen materialized. Beside that, there is a luxurious 1.9-meter bathtub that itself turns into a guest bed.

While people in other teeming cities such as Tokyo resort to drop-down beds and foldable futons, the award-winning Chang has taken the concept of space-saving to the extreme.

His tiny rectangular apartment, tucked into the bowels of an old, nondescript tenement building, has polished chrome walls that bear 24 configurations, each suiting a specific need.

The space available becomes a home theater, spa, kitchen, bedroom, chill-out zone rigged up with a hammock, depending on what Chang needs at any moment.

"The high intensity of use makes (it) more like a large home appliance than a dwelling," wrote Chang in his book "32 meter square apartment - a 30-year transformation" that chronicles the origins of his innovative abode, which has undergone numerous facelifts through the years.

Chang, who runs his own design and architectural firm, describes an empty space as a "luxury" and once built a "Suitcase House" in Beijing blurring the boundaries between public and private space.

"The only enclosed space is the toilet, and again, it's bigger than usual," said Chang, whose flat is surrounded by the highways and skyscrapers that embody Hong Kong's rampant urban development that have made spacious flats a pipedream for many.

At a cost of HK$1.8 million ($231,700), Chang hopes his dwelling offers a viable, life-enhancing alternative for Hong Kongers who can't afford anything bigger.

"The idea is to tune your home closer to what you really want instead of being dictated by the market or by the space allocated," said the designer who says he's now in talks with property developers to replicate his flat in other space-starved, costly cities across Asia and Europe, including Paris.