Sleep Attack TD takes place within a weird dream world populated by strange, impish creatures.

As someone who dreams constantly of twisted beings that drag themselves out of the crevices of my mind, I sympathise with the portly three-eyed dude that must endure the imp-y onslaught in every level.

I appreciate his resolve to keep on sleeping even as his dream-world contorts around him.

More importantly, I appreciate the interesting ideas Sleep Attack TD brings to the well-worn tower defence genre, even though the end result is fiendishly difficult (a fact that will no doubt attract avid tower defence players).

Sleep is for the weak

In some ways, Sleep Attack TD plays like a standard tower defence game. Enemies approach in waves, and all of them are intent on jumping on / disturbing the sleep of the big Snorlax-looking fellow in the middle of the stage. If a certain number slip past, you lose the round and the game ends.

As usual, the key to winning is putting down defence mechanisms like cannons, pea-shooters, and glue traps that slow down the enemies' approach. You can also upgrade on-field towers to dispatch the intruders more quickly.

Upgrades and new defences require coins, which are not easy to come by in Sleep Attack TD. Enemies drop them, and ghostly jellyfish that drift across the screen will give up a few if you manage to tap them in time.

The scarcity of coins is just one reason why Sleep Attack TD is probably better off in the hands of genre veterans.

Hard-won victories

All that said, Sleep Attack TD isn't exactly unfair. In order to succeed, players need to understand the game's unique mechanics.

The biggie is the spinning battlefield. Each stage is composed of layers that turn individually. When a group of enemies comes marching down the path to disturb the big guy's nap, you don't necessarily have to lay down a new tower.

Instead, you can turn the field around so that an unused cannon on the other side of the level suddenly proves useful.

Turning the battlefield is also an important non-violent strategy. By pulling apart and re-assembling paths, a seemingly direct route to the centre of the stage suddenly becomes a detour for the bad guys.

The reason why Sleep Attack TD is stingy with its money is because it doesn't want you to win by simply laying down as many weapons as possible. Every weapon costs dearly, so you must learn how to use them efficiently.

Moreover, it's vital to know when to scrap underused towers so you can fund other weapons elsewhere in the field.

Rough sleep

Sleep Attack TD is a challenging tower defense title that manages to add a couple of new layers to tower defense games in general. Just don't expect to be able to beat it in your sleep.