If you're looking for a new game for less than the cost of a tank of gas, we'd strongly recommend you take a look at Orcs Must Die.
Some games are triumphs of storytelling and character development. This isn't one of them. OMD tells its story through the use of static art and a bit of in-game dialog, but the title neatly summarizes the purpose of the game. There are orcs. You're a War Mage. Not a particularly bright, skilled, or experienced War Mage, mind you, but someone
has to deal with all these orcs.
Flame bracers are hard.
Robot Entertainment saved their fine tuning for the game's various maps and combat options. While it's a tower defense game at heart, OMD offers a much deeper combat experience than simply picking the right tower and plunking it down from a third-person omniscient perspective. Not only are there an array of offensive and defensive traps, there's a full contingent of spells as well. After you pick your traps, you can select a "Weaver" who offers additional buffs. Players who prefer traps and summoned creatures can choose the Steel Weaver, while those who favor a more direct approach have options to boost their ranged and melee damage output, improve spells, or increase movement speed.
Maps are bright, colorful, and varied. Also filled with death.
There's no "right" solution; no matter what you choose you'll find yourself dashing back and forth between entrances, laying traps to decimate or delay one group while you leap through a portal and fend off the other. No two levels are the same; players who assume that a long hallway is a simple shooting gallery may find themselves caught off-guard by an unnoticed entrance, fast-moving enemies who dodge most traps, or fliers who simply avoid the morass of death mounted to the floor.
I'm generally no fan of playing through a game a second time on a higher difficulty level, but OMD's Nightmare mode is great enough to make me reconsider. The second time through the game is blisteringly hard; you'll find yourself panting by the third level. That's one of the only problems with OMD; the difficulty pace is occasionally uneven, even on Normal difficulty. If a level is giving you too much trouble, the game will ask if you want to switch to Apprentice Mode. You can only earn two skulls per level at that difficulty, as opposed to up to five in standard mode, but it gives players the chance to learn the quirks of a map without being pasted by the enemy.
Your spellbook shows you which enemies will be attacking and gives a list of your assorted goodies
In between matches, you have the option to spend skulls to upgrade various traps. Trap balance is good, though the upgrade value of each trap varies. In general, we'd recommend upgrading traps with added effects (your spike trap gains a snare, the Push trap gains a short stun) more than the simple price decreases. Being able to use Push traps to stun orcs while flinging them back and forth across a hallway like a game of pinball is far more useful than simply decreasing the cost of a barricade or Steam Trap.
There are trap combos (Steam Trap + Arrow Trap is a personal favorite), giant mechanical ballista, and in the later levels, one-shot spiked logs you can release to create giant rolling walls of bleeding green death. The game never takes itself too seriously; the titular character is known to exclaim: "Aww, look who has no arms!" Notable achievements include "Giblet Storm" (self explanatory) and SG1 (for frequent portal use).
The basic game is $14.99 on Steam
, the two add-on packs (Artifacts of Power and Lost Adventures) bring the price up to $19.99.