Book about a boy testing a new VR game

Trying to remember a book I read. I’m fairly certain I got it from my secondary school library, so it would have been published before 2005 (likely 90s or early 2000s). Almost certainly paperback, but I can’t remember any details of the cover appearance.

I think the main character is a boy, who has been asked by his dad to test out the new computer game he has been working on. This is a groundbreaking new technology – a VR game, that makes you feel as if you are really present in the game. The VR system is a glasses (or helmet?) and glove affair, with the glasses to show you the VR world and the glove to let you interact with it. I think there’s also another child acting as a tester (a girl), though I can’t remember if they knew each other before starting to test the game.

The game is split up into levels, and the testers have a kind of competition to advance through the game faster. Each level has a different setting (though I can’t remember what they actually are; things like "Medieval Castle" and "Indian Temple"), and an item you need to find to progress (I’m pretty sure a Prayer Wheel is one of the items, from the temple level). As they play, they run into various scary things, and notice something curious – the scary things (spiders and suchlike) seem to be tailored to their specific fears, and the game cuts out entirely when they encounter them.

It turns out that their parents aren’t really testing the game itself, but are testing the safety devices built into the VR machines. The theory goes that VR is so realistic, anything too scary might cause real life issues (heart attacks or what have you). To protect against this, the gloves are fitted with a pulse sensor, so that the game cuts out when the player’s heart rate gets too high. The parents were deliberately using their knowledge of the children’s fears to trigger the safety cut out. The children discover this, though, and use a strip of cardboard (or something) to defeat the pulse sensor, so that they can prove to their parents that the safety device is not good enough, and would be defeated by children looking for thrills.