At times the lack of originality in coming up with a game design is almost depressing. For the past five years, the Web game and app worlds have seemed fixated on Mafia games (all based on the Drugwars model) and Tower defense games. I know designing a new game is harder than developing one that you know, but it would be good to see something a little different.

Derivative Design

Many of the original arcade games were derived from earlier games. First there was Pong, computer ping pong with two paddles and a ball. Then the playing area was turned 90 degrees, one paddle was removed. That was Breakout, where your ball knocked holes in a wall. I remember a variation of that where the walls moved slowly down the screen and had to be destroyed before they reached the bottom. A couple of years later Space Invaders appeared. Now the bricks became aliens marching side to side down the screen while you shot at them. Then a year later, in Galaxian, those aliens became ships that gently moved until formations broke off and dove to the bottom while firing at you. So there's a line of derived games from Pong to Galaxian. It's not much of a leap from Space Invaders to Frogger either. If you're about to program a Tower Defense game, here's a derivative design that appears quite different though it fundamentally plays the same game. It's yours to do with as you wish. This design was created by me and is placed in the public domain. I came up with it when I was wide awake at 3 a.m. one morning--the time when all quality games are dreamt up! I came up with it by thinking of Missile Command, a game design I really liked, and trying to re-imagine it. I've also played 2D arcade games where ships drop depth charges on submarines and submarines fire torpedoes back. So I thought about how the game might play out. The result is Ack Ack Battery.

Ack Ack Battery Game Defined

The playing area is a bit like Atari's classic Missile Command, except there's a road along which infantry, tanks and artillery slowly move from left to right. Your job is to protect the troops against enemy aircraft. You start with a single machine gun emplacement in the middle of the bottom section, placed just to the side of the road, i.e., above it on a 2D map. You gain points for tanks and troops that exit off the screen and for shooting down the attacker's planes. With those points you buy replacements guns and upgrades. The game is made up of waves of attackers, maybe something like this:.

1. Single bomber flying horizontally near the top, dropping bombs. It can fly from left to right or vice versa.
2. Multiple bombers flying near the top.
3. Dive bombers swooping down.
4. Paratroops released high, who land and start attacking troops and tanks.
5. Paratroops and parachute tanks released high.
6. Drones that nip around the screen area very rapidly, firing missiles at troops and tanks.
7. Slow release nukes that drift down on a parachute. If not destroyed before exploding, these cause a lot of damage.
8. Ground attack aircraft that fly at low altitude from right to left.

Parachute troops and tanks that land will fight your tanks and troops. Enemy tanks destroy troops without loss. If they fight your tanks, both are wiped out one for one, as are troops against troops. On subsequent levels the order of attackers repeats but:

1. There are more of them.
2. They fly lower.
3. They fly faster.
4. They drop more bombs or missiles.

There can be different types of bombers, propeller aircraft to start (such as a B-17 Flying Fortress ), then jet bombers (B-52), then stealth bombers (B-2) To help you defeat them, you accumulate points and can either add multiple weapons/emplacements or upgrade/replace existing weapons. The weapons available are:

• Machine gun.
• Dual machine guns.
• Auto cannon--nice explosion at target.
• Quad cannon--four nice explosions at target.
• Rocket--big explosion at target but slower than a cannon.
• Rocket battery--drag the mouse cursor and leave a pattern of targets.

You move the targeting cursor with the mouse and your gun tracks it. There's a slight delay between firing machine guns and cannons and hitting the target, and a longer delay for rockets. The better weapons have larger explosions and do more damage. Having animated aircraft going down in flames would be cool! Multiple weapons fire in parallel streams. Note that emplacements can be damaged by bombs and that aircraft at higher levels will target emplacements deliberately.

Building It

Implementation should not present too many problems. The main issue is game balance. This can be done by giving the enemy points and having each wave increase the point total over the previous one. If a player is doing well, then the points gained should provide enough fire power to balance the larger enemy forces in the next wave. At it's heart the game play mechanism is still that of a Tower defense game, but presented sufficiently differently. That's it. Now go code Ack Ack Battery as a Flash/HTML5 Web game, desktop or mobile app. If anyone does, please let me know. (And while it's not obligatory, a link back here would be appreciated.) Also, we might show off your game to your fellow developers.