It has been less than a week since Pokemon Go hit iOS and Android in the US and other markets, but it has already proved to be the shot in the arm Nintendo was looking for. Japan’s gaming company Nintendo Co Ltd registered a surge in shares again on Monday. Nintendo now stands at a market-value of $7.5 billion in just two days as investors cheered the early success of Pokemon GO – its first long-awaited venture in mobile gaming.Pokemon Go, which mixes a classic 20-year old franchise with augmented reality, allows players to walk around real-life neighborhoods while seeking virtual game characters on their smartphone screens. The game has earned enthusiastic early reviews.In the United States, by July 8 – two days after its release – it was installed on more than 5 per cent of Android devices in the country, according to web analytics firm SimilarWeb.It is now on more Android phones than dating app Tinder and its rate of daily active users was neck and neck with social network Twitter, the analytics firm said. The report said that the players are spending an average of 43 minutes in the game per day, which is more than time spent on WhatsApp or Instagram.As the game took the U.S. by storm, Nintendo’s shares surged by a quarter in value on Monday to their highest level since November. They have gained 36 per cent since Thursday’s close with the initial momentum coming from the game shooting to the top of free app rankings in Apple Inc’s U.S. iTunes store.The game has been released in the United States, Australia and New Zealand so far. Launches for other countries including India are due soon. However, Android users around the world have found ways to install the game on their phones using APKs.Pokemon GO may not prove an immediate boost to Nintendo’s bottom line: it is free and Nintendo is not the sole investor or creator.The game itself was created by Niantic, spun off from Google last year, and Pokemon Company. Nintendo owns a third of Pokemon Company and both have undisclosed stakes in Niantic, which had already developed a similar augmented reality named Ingress, multi-player game in 2012.Some analysts have been upbeat about the money-making potential for Pokemon GO, largely from small purchases made while playing – and the positive signs for other mobile gaming launches planned by Nintendo for 2016 and 2017.”If nothing else, PokÃ©mon GO has shown that there are ‘dormant’ Nintendo fans eager to trial its content for smartphones,” Deutsche Bank analysts said in a note.But others cautioned that there were still large question marks over whether Pokemon GO will be able to generate the kind of sustained excitement that would significantly boost Nintendo’s earnings – particularly given that the company now has to contend with a sharp strengthening in the yen.Real change, those investors say, would have to come from the core console business.”Now if we were talking about its next generation console becoming the core platform for gamers, then that would be something to get excited about – but at the moment, this alone is not enough,” said Yoshihiro Okumura, general manager at Chibagin Asset Management.