There's not a lot people can do when they switch on the television and see Cambodians badly injured by landmines. Rather than merely feeling sorry for such victims, a Form Seven student from La Salle College has gone a step further - he has invented a prosthetic leg that is cheaper and easier to use. Denis Huen Yin-fan's design won him the top award at My Favourite Inventions for Quality Living Competition organised by the government and Towngas. 'I was watching TV and saw these people who had lost their legs to landmines,' Yin-fan said. 'Most of them were helpless because they couldn't afford prosthetic legs, which cost hundreds of thousands of dollars each,' he said. Yin-fan's device costs $2,000 - the current market price is about $200,000 - and took four months to make. It uses a pressurised pump with gas to give more strength to the prosthetic leg which moves with ease. Yin-fan said the concept originated from a 'little thing' he noticed in daily life. 'I saw an oil-pressurised loading truck on the street, but I used air instead,' he said. There is a sensor attached to the prosthetic limb which is fitted to the other leg. 'Then both legs can move smoothly,' he said. Yin-fan showcased a model of his design at the Innovation Expo 2005 last week. The four-day exhibition, organised by the Innovation and Technology Commission, featured advanced designs by local colleges, schools and companies. Primary students, too, had the opportunity to display their creativity and scientific knowledge. About 20 Primary Six students from St Paul's Co-educational Primary School set up an exhibit called Crocodile Carnival at the expo. It aimed to remind the public that crocodiles could be extinct by 2010 unless urgent steps were taken to protect them, according to Sonia Wu Sau-ching, a member of the St Paul's team. There were light- and sound-activated robots, together with a short film on environmental protection. There was a robotic team of lion dancers as well as a crocodile model which could rotate 360 degrees. People can easily visualise robots but turning them into real ones is a different story, according to St Paul's student Bess Chung Ka-wai. There were times when their robots fell into pieces when they were activated, Ka-wai added. The sophisticated parts, such as sound and light sensors, came from their own toys - Lego's Mindstorms series. In addition, visitors enjoyed Youth Day on Sunday, which included an internet robot contest and workshops aimed at raising interest in innovations and technology.