It's rare to see a game that's made entirely of boss battles. But in smartphone games it makes a lot of sense. No preamble, no carefully managed expectations - just a series of short, impressive fights.

That's the angle Raid Leader is aiming for, and it pulls it off well. A clever, diluted mix of RPG and RTS, it offers a parade of increasingly tough fights as you strive to liberate a fantasy kingdom.

There's no grind, and no real story to get in the way. It's just you, your three intrepid warriors, and a cavalcade of gargantuan bad guys to hack into pieces.

Not so horrible bosses

The setup is a simple one. You control three different characters - a Warrior, a Wizard, and an Archer. Each has his own unique skill set, and each is a vital part of your boss killing machine. If one of them falls, it's likely the rest will follow suit soon after.

Your Wizard can heal your characters, but it takes a minuscule amount of damage to kill him. The Warrior is your tank, a brutish oaf who gets in the face of the boss and takes as much damage as possible. The Archer hides at the edge of battle, firing her bow and controlling things with debuffs.

It's a neat, streamlined system, and one that rewards clever play. Movement and attacking are controlled by pressing on a hero and sliding your finger to the desired target, and special moves are unleashed by tapping a bar along the bottom of the screen.

Raid leader, you've got a bogey on your tail

Those special moves are bought using the gold you receive for defeating a boss. You can only have two equipped for each character at a time, so getting the right balance in your team is essential.

Fights start off reasonably sedately, but soon progress to smart wars of attrition. Some bosses call minions to attack you, while others release spores that you need to tap to kill. The game always lets you know what's coming, and juggling attack and defence becomes a hectic and addictive struggle.

Two arenas, unlocked as you progress through the game, allow some respite from the boss-slaying, letting you kill as many minions as you can to earn some precious gold.

Victory pa-raid

Raid Leader doesn't give you an easy time of it. Its attractive cartoon veneer hides a game that's quick to punish the unwary player, and the tide of battle can turn from comfortable victory to tragic defeat in the blink of an eye.

You need to understand your team, and make sure you're prepared for everything the next boss is going to throw at you. Learning from your mistakes is essential, and sometimes back-tracking to earn more gold for a re-spec is your best move.

Addictive and attractive to look at, Raid Leader is a game that fits a lot into its relatively small playing time. A few more fights wouldn't go amiss, but this is an impressive package for anyone looking to fit some boss battles into their spare time.