If there's one thing that kids love more than Tetris, it's learning about the security features built into new banknotes. Thankfully, the folks at the European Central Bank have devised a way to combine both of those pursuits in the form of Tetris New 20 Euro. The browser-based title is a variation on the block-dropping classic that sees you learn security facts about the new 20 Euro note as a reward for finishing a level. For instance, did you know that the portrait of Europa (pictured) becomes a transparent hologram if you hold the note up to the light? Put it this way: with trivia this good, no-one will be able to resist you hitting on them at the club this weekend.