At the risk of bombarding you good people with tower defence games in these happy times of Plants vs Zombies and ridiculously cheap Defence Grids, let's throw another one into the mix. Don't roll your eyes at me like that, young man - this one is free and ingeniously different.
Element TD is a tiny mod for Warcraft III that adds a new scenario map, playable either as singleplayer or a sort of race/survival-based multiplayer. Clearly, the meat of it is constructing a warren of turrets to protect your base against a horde of invading Warcraft-universe men, monsters and elementals, but the construction system is a whole lot more complicated and thoughtful than the insta-plonk building of most tower defence games. Oh - and I'm not saying this is BRAND SHINY NEW NEWS. I know Warcraft 3 TD has been around for ages - it's just what I was playing yesterday, and on RPS we write about what we play.
Towers types are divided into a bunch of elements - Earth, Water, Light, Dark, Nature, Fire - each of which is better against certain enemy types. A mixture of logic and knowledge of Warcraft lore establishes which is shotgun to the creeps' rock and paper, though frankly it becomes as much about creating a massive pile-on of turrets rather than arranging elaborate exact matches. The really fun bit is when you come to upgrade the towers - you can either bump, say, your Water tower up a level, or you can combine it with, say, a Fire element to create a Vapour tower. Or with whatever else to create something different entirely. After that, again you can do a straight upgrade, or you can add a third element to create a brand new tower type. And that's how you end up with a vast array of damage, area of effect, slow-down or life-restoring towers.
Added to that is the RPG-like collection and levelling up of the core elements - after every five waves of enemies, you're rewarded with an element of your choice, which involves taking down a boss unit. So, you have to plan your build order way in advance rather than simply buy bigger stuff as your wallet swells. It's clever stuff, and the huge, crazy variety of units and turret types makes for a very pretty, if truly chaotic, vista of carnage.
In multiplayer, each guy takes command of their own battlefield, which is in turn besieged by the same beasts simultaneously, and tries to last as long as possible. In the event of a stalemate, well - that's when Ronald McDonald attacks.
Fun, challenging, ridiculously over the top and only 1.2Mb. Get it here.