Fire artillery shells to blow up the enemy with Mark Vanstone’s take on a classic two-player artillery game
To pick just one artillery game is difficult since it’s a genre in its own right. Artillery simulations and games have been around for almost as long as computers, and most commonly see two players take turns to adjust the trajectory of their tank’s turret and fire a projectile at their opponent. The earliest versions for microcomputers appeared in the mid-seventies, and the genre continued to develop; increasingly complex scenarios appeared involving historical settings or, as we saw from the mid-90s on, even offbeat ideas like battles between factions of worms.
To code the basics of an artillery game, we’ll need two tanks with turrets, a landscape, and some code to work out who shot what, in which direction, and where said shot landed. Let’s start with the landscape. If we create a landscape in two parts – a backdrop and foreground – we can make the foreground destructible so that when a missile explodes it damages part of the landscape. This is a common effect used in artillery games, and sometimes makes the gameplay more complicated as the battle progresses. In our example, we have a grass foreground overlaid on a mountain scene. We then need a cannon for each player. In this case, we’ve used a two-part image, one for the base and one for the turret, which means the latter can be rotated using the up and down keys.
SPACE bar is pressed, we call the firing sequence, which places the projectile at the same position as the gun firing it. We then move the missile through the air, reducing the speed as it goes and allowing the effects of gravity to pull it towards the ground.
We can work out whether the bullet has hit anything with two checks. The first is to do a pixel check with the foreground. If this comes back as not transparent, then it has hit the ground, and we can start an explosion. To create a hole in the foreground, we can write transparent pixels randomly around the point of contact and then set off an explosion animation. If we test for a collision with a gun, we may find that the bullet has hit the other player and after blowing up the tank, the game ends. If the impact only hit the landscape, though, we can switch control over to the other player and let them have a go.
So that’s your basic artillery game. But rest assured there are plenty of things to add – for example, wind direction, power of the shot, variable damage depending on proximity, or making the tanks fall into holes left by the explosions. You could even change the guns into little wiggly creatures and make your own homage to Worms.
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