P 009 – Game Over Man!

CoCo Cosmic Aliens 0.13 with source code discussion

The latest iteration of CoCo Cosmic Aliens adds a game over/attract mode, and include double buffering again.

Progress is being made, but not as much as I had hoped for this version, but progress nonetheless.

The ability to die now exists. An initial high score of 10,000 points has been added to the game, and the ability to beat the high score now exists.

The extra life routine has been tweaked. Originally Extra life was first awarded at 3,000 points and would increment by 3,000 each time. I’ve tweaked that to increment by “WAVE x 1,000” so if you get an extra life on WAVE 5, it would add 5,000 points to the next extra life you’d receive, etc.

I’ve decided to give a peek into the source code/logic and routines in this video preview, I’ll also share the actual text of my “cheat sheet” document in this post:

Here are my programming crib notes:

Top Minimum location = 16 (Y)
Bottom Maximum location 159 (Y)
16x12 grid using full 16x16 blocks for cells
Pmode 1,1-1,2=page1
Pmode 1,3-1,4=page2
pmode 1,5-1,6=page3
pmode 1.7-1,8=page4

GET/PUT variables:
A1-A8=Aliens, R1-R5=Rocks, CR=Blank space TL=TOP LINE, BLANK OUT STATUS BAR
EX=Explosion, SP=Spaceship, UF=UFO, L=Laser, B=Bomb
CA=Current Alien, MA=Maximum Aliens
ES=Enemy Sate (which enemy to display, of the 8 available sprites)
FB=Fire Button, Peek 65280

AX,AY(8) = alien x/y coordinates
BX,BY(8) = bomb x/y coordinates
BS(8)=Bomb State ON/OFF
CB=CURRENT BOMB
RX,RY(8) = Rock X/Y coordinates
SX,SY(8) = Shot X/Y coordinates
SS(8)=Shot State ON/OFF
RL(8)=Rock Lives
RF(8)=Rock Falling Rate
UX,UY=UFO X/Y Coordinates, US=UFO STATE
X1,X2(15),Y1,Y2(15), ABSOLUTE X/Y COORDINATES OF SPRITE LOCATIONS
TX,TY(32) TEXT X/Y COORDINATES
PS=PLAYER SCORE WV=WAVSAVEE SR=SHIPS REMAINING EL=EXTRA LIFE POINTS TO REACH

Joystick: Peek(65280)
126/254=right buttonLIST
125/253=left button

100-110 SET INITIAL VARIABLES + RESET ALIEN POSITIONS
120 CLEAR SCREEN START GAME:CLEAR SCREEN, INCREMENT WAVES/ALIENS UPDATE STATUS BAR
139 MAIN GAME LOOP
205 ALIENS CHANGE DIRECTION
265-300 ALIENS CHANGE DIRECTIONS
305-340 PUT ONE OF 8 ALIENS ON SCREEN
345 TURN LASER SHOT ON
365 PUT LASER SHOT ON SCREEN
390 TURN ON BOMB DROP
410 BOMB FALLING
440 SPACESHIP HIT
470 BOMB HIT
495 ALIEN HIT LASER
521 LASER HIT ALIEN
525 NULIFY LASER SHOT
580 RENDER TOP STATUS BAR
581 UPDATE SCORE
582 UPDATE WAVE
583 UPDATE SHIPS
584 UPDATE GAME OVER
585 UPDATE HIGH SCORE
590 TEXT RENDER
605 PCOPY COMMAND
610 REFRESH ALIENS/SCREEN
615 RESET BACKGROUND ARRAY
620 INCREMENT WAVE COUNTER
625 INCREMENT/CYCLE ENEMY IMAGE
630 (RE)SET ENEMY STARTING POINTS
635 DECREASE ALIENS LIST
640 JOYSTICK ROUTINE/SPACESHIP PUT
650 UFO ENABLE
655 UFO MOVE LEFT/RIGHT
670 UFO HIT
680 EARN EXTRA LIFE
685 ERASE UFO
686 PUT UFO
690 WAVE BONUS

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