It is rare for the human race to make a billion of anything, still rarer for any one company. But Logitech claimed to have shipped its one billionth mouse, just ahead of the device's 40th birthday this month. Even if the PR men had a hand in this "wonderful coincidence", the number is roughly right. Add in other firms, and it starts to seem like electronic mouses (the plural in many dictionaries) will soon outnumber mammalian mice. Yet with middle age, comes concern about long-term health. Touch screens, track pads and even facial recognition are all talked up as replacements, with Bill Gates predicting the imminent death of the creature. That would be a pity, for the sensation that started when Douglas Engelbart showed off a wooden-block mouse at Stanford in 1968, is at root a beautifully simple idea. Controlling things with the hand is intuitive, so the mouse opened up computing to non-nerds, using all manner of means to put them in charge. There were trackwheels, then rubber balls - which allowed smoother movement, but got gummed up with dirt - and now mini-cameras that film the table top. It was not the farmer's wife, but the mini-radio transmitter which cut off their tails, rendering newer mouses wireless. Clicks, drags-and-drops, and right buttons are now part of everyday life. The latest phone interfaces are as tempting to us as a morsel of cheese to a mouse, but they remain infuriatingly fiddly. To kill off the mouse before perfecting a replacement would be to walk into a trap.