Subject: [stella] Alpha version of my game|
From: emooney@xxxxxxxxxxxxxxxx (Erik Mooney)
Date: Thu, 10 Apr 1997 02:26:20 GMT
Attached in MIME format is the current state of my game. It's a Space Invaders clone, using playfield graphics to display an 11x5 matrix of invaders instead of the 6x6 of the Space Invaders we all know and hate =) In its current state, Game Select toggles between single-player and two player simultaneous modes, and Game Reset begins a game.. the B/W and difficulty switches are not yet used. And there's no sound yet. Try this out and let me know what happens. It works fine on PC Atari and on a Supercharger attached to my 4-switch NTSC 2600. I'd appreciate it if someone would tell me what it does on PAL systems. (I'll probably implement the B/W switch as a PAL/NTSC switch eventually.) Please don't distribute the game beyond here yet, though. Tech notes: It uses simple player graphics to display the players, and repositions them with multiple copies (if necessary) to display the number of lives remaining (idea stolen from Defender.) The missiles are used for the players' missiles, naturally enough... the ball is used for the invader bombs, and it can be recycled up to 5 times to display 5 bombs simultaneously (as always, no two bombs in the same vertical zone.) Everything is displayed every frame - there's no alternating-frames logic for anything. Known bugs/limitations: I don't yet check for collisions between enemy bombs and players.. that's cause playing the game would be just too hard in its current setup.. suggestions welcome =) I haven't implemented scores yet either.. I plan to use the playfield to do that, at the top of the screen. I'm going to add a saucer, too, as all Space Invaders games should have =) When the second player's missile should be disabled, it gets displayed at the top of the screen instead... this will be fixed when I add score display. Does not affect gameplay. When an invader bomb is due to begin its display on the same scanline as an invader is being displayed, it gets skipped for that frame. This is because there's no time to set RESBL during a scanline in which I'm writing to the playfield registers six times. This is hardly noticeable, though. The bombs change color on different scanlines along with the invaders.. this gives a very nice 2600 feel to it (see Super Breakout), so I don't plan to change it =) Each successive wave begins lower down than the previous; there is no limitation on this, so eventually the waves will start so the bottom row of invaders is at the level of the players.. this will screw up the scanline count so the display will lose sync if you play long enough. There are no "shields" above the players, nor will there be.. they would be extremely difficult to implement with the setup of my screen kernel.
Description: Binary data