With Plants vs. Zombies out today, it seems like a good time to point out that there's a free downloadable demo on the official site for PC or Mac.
It's 26MB and gives you a taste of PopCap's ingenious new spin on tower defence, which costs GBP 14.95 from the same page and picked up a 9/10 score in today's review.
As the name suggests, Plants vs. Zombies pits the forces of agriculture against the forces of evil. You position Pea Shooters (guns), Wall-Nuts (barriers) and other puntastic weaponry to intercept the right-to-left advance of the undead.
It's a deceptively simple version of games like Fieldrunners, then, but it's very, very well done, with elements like resource-gathering (sunlight, of course), separate day and night arsenals, moreish mini-games and thoughtful enemy design.
It's also got the best help screen in recent history. And Michael Jackson.