A pair of Swiss policemen cast a suspicious eye as a creature in a space helmet with a camera mounted on top and carrying an astronaut's backpack wanders around Basel's St. Johann Park.

But what appears to be a visiting extra-terrestrial turns out to be a maverick designer, Jan Torpus, who is pushing the boundary between the real world and fantasy in a project he calls "augmented reality."

Through the plastic screen of his helmet, Torpus tells a pair of bemused park cleaners he sees ordinary trees, bushes and benches -- but the landscape is also populated with virtual animals which are hunting beetles.

"Perhaps we can get them to hunt our boss," one of the cleaners mutters to his colleague.

Yet a journalist trying on the helmet saw something startlingly different: a big red fish chased beetles through what looked like cane fields, which then became a desert that was then transformed into a tranquil meadow.

A massive green worm cuddled up to the fish, to the accompaniment of a dramatic movie-like musical score.

Torpus explains that in his lifeClipper 3 project, the person wearing the helmet creates their own perceptions.

"You thought the worm and the fish wanted to fight, but they are actually friends," says the 45-year-old.

"Every walk is unique: the situation in the park is always different in terms of time of day, light, weather, temperature, encounters with people and animals. The real climate is juxtaposed with a virtual climate, the real living beings with virtual ones.

"Both worlds can be influenced by the user. At the same time the element of chance plays a part in both the real and the synthetic worlds. This gives rise to unique, non-reproducible situations," explains Torpus.

Perceptions are influenced by the movement of animals and from music that is conveyed by programme in a computer strapped to the wearer's back.

Torpus's base is the Institute for Research in Art and Design (HGK) attached to the University of Applied Sciences Northwestern Switzerland in Basel, a city bordering both France and Germany.

-- 'Between daily life and fantastic worlds' --

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His project started in 2003, bringing together artists and scientists in the quest for mind-challenging sensations and new ideas for mobile phone apps, electronic maps and smarter websites.

The equipment used in lifeClipper 3 is all "off the shelf" from local electronic stores, says Torpus proudly, as he fires up a hefty Dell laptop that is strapped to the wearer's boot.

"We have to use such a bulky laptop as we need a lot of computer power to run this," he explains.

There is a Trimble GPS that provides a professional level of positioning used in in engineering and construction, surveying and agriculture. There is also a direction sensor and a biofeedback sensor strapped to the chest of the wearer.

Then there is a head mounted display with a camera and headphones along with a microphone and finger mouse.

"We scanned St. Johann Park and a 3D model was constructed" upon which all the self-generated images are projected, Torpus says. "We used the design approach of the 'game world' but the staging should stay close enough to the familiar to be perceived."

Torpus invites visitors to walk around the park with the helmet to test alternative reality.

"It shifts between daily-life conventions and fantastic parallel worlds," he says enthusiastically. "It is an alienation of physical and cultural rules like earth-centeredness, gravity, the notion of time and space."

Such talk is a little too much for a smartly-clad woman who walks by.

"We already have too much made-up reality as it is," she snaps, before beetling off.