Design

The Battle Tank MIDlet is an arcade-style shoot 'em up ("shmup") game where the player's objective is to defend the base and destroy all enemy tanks. Battle Tank is distributed as a trial version.

The main features of Battle Tank are:

• Destructible game world

• Large levels

• Various types of enemy tanks

• Bonus items (a grenade destroys all enemy tanks, a star makes the player's tank indestructible for short time, and so on)

• In-app purchase option to buy the full game (only from Battle Tank version 1.1 onwards)

To ensure the best possible gaming performance on mobile devices, Battle Tank has been designed to:

• Avoid heavy calculations

• Use UI components provided by the device platform (Sprites, TiledLayers, LayerManager)

• Use multiple threads to ensure that the UI responds smoothly

Battle Tank supports multiple resolutions and both touch and key input.

Figure: Battle Tank trial version at medium (240x320) and low (128x160) resolutions

Battle Tank version 1.1 introduces an in-app purchase feature that allows the user to update the trial version of the game to full version via a Nokia Store purchase. If the user has previously purchased the full game from Nokia Store but does not currently have it on their device, they can restore the full game for free. The full game includes new levels, new bonuses, and new enemy tanks. The in-app purchase feature uses built-in DRM to protect the full game content, meaning the content is stored in DRM-protected form within the MIDlet and unlocked with DRM keys received from Nokia Store as part of a purchase or restoration request.

In the trial version, the main menu includes a FULL VERSION option, which takes the user to the in-app purchase menu, where the user can either BUY the full version or RESTORE an already purchased full version. The purchase process is forced to automatic restoration, if applicable, so it does not matter if the user accidentally chooses PURCHASE when already entitled to the full version.

Figure: In-app purchase menu with options to buy and restore (left) and full game main menu after purchase (right)

For information about implementing the Battle Tank MIDlet, see section Implementation.