Space Invaders:

Built by Taito in 1978

Designed By Toshihiro Nishkado

Game Design:

Plot:

The game space invaders has a simple plot line. Alien invaders have come to Earth. The player is in control of missile cannon and must destroy all of the Aliens before they reach Earth.

Game Play

The Player controls a cannon that moves back and forth on the X-Axis near the bottom of the screen. (Note: I have yet to decide whether the player will control a spaceship or a ground based cannon. There will be no difference in gameplay, only in background and the player’s character.) The player one has three controls, left, right and fire. The players objective is to destroy all of the Aliens before they reach the bottom of the screen. The player receive points for destroying the Aliens and for beating missions quickly. There will be about 40 Aliens on the screen at once (normally there are 60, but this will depend on how the game looks in the small display) The Aliens also move along the X-Axis, all at the same rate of speed. As time progresses the Aliens move down the Y-Axis towards the player. While the player destroys more Aliens, the Aliens move faster. The Aliens drop bombs at the player which will kill the player if they are hit. Once all of the Aliens in a mission have been destroyed, a new mission begins with the Aliens slightly lower. There is not winning for player as the player will always die at some point in the game. The goal is to get the highest score.

Additional Gameplay Ideas(ranked in order of likely hood of appearing in game):

1. Occasionally there will be power ups that fall from the top of screen. If the Players ship runs into these power, they will get a special bonus. This maybe either a shield that allows the Player to withstand more than one hit, a limited use weapon or something that affects the Aliens negatively. Pros: Adds an extra element to the gameplay. There is a risk in getting the power ups because you may have to move close to an Alien bomb. Also, shooting the power up destroys it, giving players who aim a slight advantage. Cons: Games like Space Invaders work because of their simplicity so adding features might take away from fun. The power ups will have to be rather large in order to distinguish between them. Third, this will mess up the balance of the game, giving the player an advantage.

2. Some of the power ups will have negative effects. They will slow down the player and their rate of fire. These negative power ups will look similar or identical to normal power ups, presenting the player with a risk an increased risk in getting power ups. Pros: Helps balance the power ups and adds a little bit strategy to the game, forcing players to figure out how they need to risk. Cons: Could actually change balance back to the AI. Might make the game too complicated when compared to normal Space Invaders.

3. Include special “Boss” Aliens. These would have higher hit points(requiring two or three missiles to destroy), move faster and have a faster rate of fire. They would also move more randomly, not just from left side of screen then back again. They would not decend, and therefore can only win by killing the player. Pros: Adds a challenging aspect to the game. Cons: Getting the balance right would prove difficult.

4. Change the entire aspect of the game. The player is now a mercenary for hire. The score is replaced by money and at the end of each turn the player can purchase upgrades, similar to those given by power ups. Pros: Add a new element to the game which would make it stand out from other Space Invader clones. Add more strategy to the game as the player must decide what to buy and when. Cons: Could destroy part of what made Space Invaders fun. Again, balance would hard to figure out. Stops the constant action of the game.

The basic rules of the game are as follow:

-The Player can only move along the X-Axis on the ground. 

-The Player will have a limited speed, which might change during the game. 

-The player will fire missiles at the Aliens.  These missiles have limited velocity and limited rate of fire, both of which may vary during the game play.

-The player has an unlimited amount of missiles.

-If a missile hits an Alien, the Alien will die.  This may not include a special kind of Alien, such as a boss Alien who may have more hit points.

-The missiles cannot travel through the shields or Aliens or Alien Bombs or PowerUps if they are included in the game.

-The Player shall have three lives.  During the game, extra lives may be rewarded.

-The Player shall beat a mission when all of the Aliens have been killed.

-The Player will receive certain point values for killing each Alien.  Also the Player will receive additional points for completing the mission quickly. (Note: In original game, scoring was actually based off of how many shots between each kill. These results were looked up in a Hash Table)

-The shields can be destroyed both by the Aliens bombs and Players Missiles.

-The Aliens will also move along the X-Axis.  They will all move at the same speed in order to avoid collision

-The Aliens shall drop down the Y-Axis closer to the Player as time passes.

-The Alien’s velocity shall increase as the number of Aliens decreases.  This shall be on a set amount, not increasing for each Alien killed.

-The Aliens shall drop bombs on the Player.  If this bomb hits the Player, the Player dies.

-Only the Aliens at the bottom of each column may drop bombs.

-The rate of fire for the Aliens increases with their speed, although it may not be 1:1

-If the Aliens reach the ground, the Player shall lose.

-If all of the Aliens are destroyed, a new level will be launched.  The Aliens will be closer to the Player in later levels.

-This is a certain death game meaning that there is no last level. The game simply becomes more and more difficult, to the point where the limitations of the Players speed and rate of fire force him to lose.

Special Rules(May not be included in final game)

-There shall be at random times power ups for the Player to collect and use.  These power ups include missile upgrades (increase velocity, increase rate of fire), new, limited use weapons (a missile spread that shot out in a triangular formation, constant use laser weapons to sweep through the aliens), change the current state of the Aliens (move them back up a level, decrease their Velocity and rate of fire), limited time shield so that the Player can be hit more than once without dying, or possible an extra life.

-More than one power up cannot be used at the same time.  If a user has a power up active when he get another one, the new power up will be turned active, while the old power up will be lost.

-There shall also be negative power ups.  These will either be made to look similar to the normal power ups or identical to other power ups, but with a smaller chance of appearing (something like 1 in 6 power ups will be fake).  These will have the opposite effects of the power ups(slower velocity, slower rate of fire, slower missiles)

-If a player has an active power up when they receive a negative power up, they will simply lose their current power up.

-If a player has a negative power up when they get a normal power up, the negative power up will be deactivated.

-There shall be other special items, which if enough is collected grants the player a new life.  These will be like coins in Mario, although less frequent.

-Missiles will destroy power ups and extra life coins.

-There will occasionally be a “Boss Alien”.  This Alien will be able to withstand more than one hit by a missile.  It will be faster than the other Aliens and have a higher rate of fire.  It will occupy the first top row of Aliens.