Haunted House Eyes

[Bill Lange]

I was bored at work today and wrote a few hundred lines of assembly code with the Atari Assembler/Editor cartridge that copies the "eyes" from the 2600 game Haunted House.

 

Is anyone willing to look at the code and critic the Joystick routine and the code that changes the "eyes" bitmap data when the direction of the joystick is changed?

 

Basically the joystick code reads the joystick and if its $F, it centers the eyes, if not, it JMPs to check to see if left ... then right ... then up ... then down.

 

Seems like I should use a table indexed by the joystick position value or something more effiecient.

[Heaven/TQA]

yes.

 

karolj_nadj@web.de

[Bill Lange]

Here is my joystick reading routine -

 

Seems there should be a more effcient way of handling it. Also, since I change my bitmap depending on the JS direction, I need to check to see if the direction changed since the last time through ... if it hasn't, no need to re-image the bitmap. What do you think.

 

 

1390 ; READ JOYSTICK

1400 ;

1410 RDSTIK

1420 LDA #4

1430 ORA PACTL

1440 ;

1450 LDA STICK0

1460 CMP #$F; stick centered

1470 BNE JSRIGHT

1480 LDA #$0

1490 STA EYEOFS

1500 JSR DRAWPL

1510 JMP RETURN

1520 ;

1530 JSRIGHT

1540 CMP #$07

1550 BNE JSLEFT

1560 LDA #$14

1570 STA EYEOFS

1580 LDX HRZPTR

1590 INX

1600 STX HRZPTR

1610 STX HPOSP0

1620 JSR DRAWPL

1630 JMP RETURN

1640 ;

1650 JSLEFT

1660 CMP #$0B

1670 BNE JSDOWN

1680 LDA #$F

1690 STA EYEOFS

1700 LDX HRZPTR

1710 DEX

1720 STX HRZPTR

1730 STX HPOSP0

1740 JSR DRAWPL

1750 JMP RETURN

1760 ;

1770 JSDOWN

1780 CMP #$0D

1790 BNE JSUP

1800 LDA #$A

1810 STA EYEOFS

1820 INC VRTPTR

1830 JSR DRAWPL

1840 JMP RETURN

1850 ;

1860 JSUP

1870 CMP #$0E;

1880 BNE RETURN

1890 LDA #$5

1900 STA EYEOFS

1910 DEC VRTPTR

1920 JSR DRAWPL

1930 JMP RETURN

[Bill Lange]

I guess this should be moved to the programming section ....