the cutting room mirror

Head On

Head On is the first dot-collecting maze game, coming out over a year before Pac-Man. Of course, as you can see from the title screen, it's not much of a maze, and you run over the dots instead of eating them. Eleven years later, it got immortalized in the memory of every Sega arcade operator thanks to a downsized clone being stationed on every JAMMA board purchased, exploiting a loophole in Japanese laws that forbade developers from selling cabinets without any games.

Filler Text#

There's filler text at the end of the game ROM. The text differs depending on the game version:

Head On (2 Player)
(MAME: headon)

Head On (1 Player)
(MAME: headon1)

Alpha Fighter / Head On
(MAME: alphaho)

;MODS FOR 2 PLAYER
;8/31/79
;9/5/79
;9/6/79
;ERASE BONUS

FBONUS:
LD HL,PLAYER
BIT 0,(HL)
LD HL,153.341
JR Z,EBON1
LD HL,157.341
JR EBON1

EBONUS:
LD HL,PLAYER
BIT 0,(HL)
LD HL,253.341
JR Z,EBON1
LD HL,257.341

EBON1:
LD A,PBLANK
LD BC,6.2
JP BOARD

;**

;PUT "BONUS"

QBONUS:
LD HL,PLAYER
BIT 0,(HL)
LD DE,13.13
JR Z,QBON1
LD DE,17.13

QBON1:
PUSH DE
LD BC,6
LD HL,BN1MES
CALL PUTMES
LD BC,6
POP DE
INC D
JP PUTMES

PBONUS:
LD HL,PLAYER
BIT 0,(HL)
LD DE,13.15
JR Z,PBON1
;**

INIT:
SUB A
LD (LANCNT),A
LD (DILANE),A
LD (DICNTR),A
LD (DIFLAG),A
;AR SIDEWAYS

EV6:
LD IX,CCTAB
LD A,3
LD (TCAR),A
LD A,(ADVERT)
AND A
JR NZ,EV6G

;CHANGE BITS TO DIR

EXX
LD E,(IX+JOY)
LD B,4
LD C,0

EV6F:
RR E
CALL C,TSTDIR
JR C,EV6E
INC C
DJNZ EV6F

EV6E:
LD (IX+JOY),C
EXX

EV6G:
LD HL,SFT2
LD A,S1

;**  ALL CARS SIDEWAYS

EV6C:
EX AF,AF'
LD A,EV5CLK
LD (BC),A
LD A,(IX+PAS)
CP 2
RET C
CALL SERV

;GET DIR

LD A,(IX+JOY)
CP 4
JR NC,EV6D
LD C,A
CP (IX+DIR)
RET Z
INC A
INC A
AND 3
CP (IX+DIR)
RET Z

;SCREECH SOUND

EX AF,AF'
CALL SNDON

;MOVE SIDEWAYS
;C=DIR

LD A,C
CALL NEWDIR
CA
STACLE

LD (IX+COL),0
CP HWALL
JR Z,EV6A
CP VWALL
JR Z,EV6A
CP PBLANK
JR Z,EV6B

;OWN CAR?

CP 15
JR NC,EV6H
LD A,(TCAR)
CP 3
JR NZ,EV6B

EV6H:
LD (IX+COL),1

EV6B:
CALL UMOVE

;RESTORE FORWARD DIR  

EV6A:
LD