When it comes to user interfaces, some things are best controlled by a keyboard and a mouse, some by two joysticks, and a few important things by a big red button protected by a glass cover, apparently best broken by a lady's stilleto heel.
Still, who would have thought the best way to control a monkey throwing darts at balloons was with your index finger?
We only mention this because of our initial scepticism when we heard popular web game Bloons was making the journey to iPhone. A game that seemed ideally suited to a large monitor and mouse interface, we thought the experience would be overly compressed on a 480x320 touchscreen.
Happily, we'd now argue Bloons on the iPhone is the definitive version.
The main reason for this is the iPhone version's control mechanic, although it takes a while to get used to this as initially you tend to start your throw on the wrong place on the touchscreen.
This is important because while you rotate your fingertip to provide the direction of the throw - as demonstrated by a graphical arrow so you can properly aim - the power part of the equation is controlled as you then pull your finger along the direction of the throw. Start too close to the right or top edge of the screen and you run out of real estate.
It matters because Bloons is a game where the strength of your monkey's throws is vital. The graduation between a small lob and full power rocket isn't linear, which is why during the opening levels you'll tend to underestimate how hard to throw your darts. It's only when you decide to get seriously into balloon popping that you also get into the swing of things.
This process is aided by the level design. There are 50 levels in total, and the first few are quite tutorial in tone, but you'll soon be dealing with examples that make your mind ache. Bloons isn't a traditional puzzle game, but as elements such as bomb balloons, triple shots, rubber bricks and ice balloons are brought into play, the layering creates situations where your shots have to be perfect to succeed.
A good example of this is Way Home (9), which forces you to perform two subtlety different drop shots onto a rubber sheet in order reflect your dart around the corner and clear the required number of balloons. Helping you make these sorts of shots is the way in which your previous shot is ghosted by a transparent blue arrow, showing you its power and direction and allowing you to make small adjustments.
Another great level is Sunroof (27). As you fire one dart, kickstarting a destructive process, you have to fire your second dart before that process has come to an end.
Of course, the majority of such levels are one shot wonders, with little replayability, but there's a decent balance between them and the more standard experiences. You can go back to most cleared levels and try to increase your percentage popped total because you don't typically have to clear all balloons on a level, only a set number.
And actually this is one of the game's best tricks, as you'll often 'crack' a puzzle only to discover you've done it incorrectly, or now have to solve another set-up.
Still, the one issue we have with Bloons is the occasional coding oddity in terms of collision detection between the darts and the environment. It's not that the travelled trajectory is incorrect, only that the graphical representation makes it look wrong.
Other than this however, the only criticism can be that 50 levels just isn't enough, but we'd assume another set will be available soon.