Start digging into the world of Minecraft and you might find yourself getting into something much more time-consuming than you expected.
Computer games have got more impressive in recent years - to the point where virtual characters look almost real.
It's odd, then, to find a game that's taking the internet gaming community by storm - but looks as though it has stepped out of a time machine from the late 1990s, with blocky, pixellated graphics of the sort your dad used to play when he was a kid.
The game is called Minecraft, and your character is the miner: A digger and builder of wonderful things.
The basic Classic version dumps you in a randomly-generated world of blocks, with God-like powers to build whatever you like. You have unlimited supplies of materials and can create anything you wish out of stone, earth and wood.
But upgrading to Alpha mode adds much more: Here your materials are limited and there's a day-and-night cycle - and after dark, the monsters come out.
Unlike most other games, these monsters are to be feared. If they catch you, that's it, you're done for. You don't get three lives. It's up to you to use your wits, and the basic materials in the world around you, to survive.
The result is a game which thrills the player without the need for fancy graphics or 3D gizmos. Minecraft is a game you enjoy for the playing, not for the watching.
Everything about Minecraft is different: It's been made almost single-handedly by one young programmer, Markus Persson, completely independently of the huge games industry.
Also it's free to start playing, and very cheap to upgrade to the full version - which more than 600,000 people have already done.
To get started with your building, visit www.minecraft.net. Try out the free online version before downloading a copy to play on your own computer.