Alien-A
Descripción del contenido de la página
Juego de invasores escrito en Z80 para la Sinclair ZX Spectrum.
Etiquetas:
Escribí Alien-A en 1986, como un ejercicio para hacer una versión mejorada en Z80 de un juego escrito en Sinclair BASIC. El juego original en que me inspiré (3.47 KiB), anónimo, apareció publicado en el año 1983, en las páginas 14 y 15 del primer número de la revista ZX:
(190.87 KiB)
(209.71 KiB)En mi versión mantuve los gráficos de un carácter y el movimiento por líneas y columnas; en ese sentido no me compliqué nada. Sin embargo cambié casi por completo el desarrollo del juego, hasta el punto de que lo único que quedó del original fue el paisaje y la forma de la mirilla.
En 2010, para publicar el programa en programandala.net, rescaté el código fuente original, que conservaba en un fichero TAP en el formato del ensamblador GENS3, y con unas sencillas manipulaciones con ayuda del editor Vim convertí el fichero TAP original en un fichero de texto preparado para ser compilado con Pasmo. Mi intención sólo era facilitar la publicación del programa, pero cuando tuve entre mis manos (mejor dicho entre mis teclas) el código fuente en un formato «moderno» no pude resistirme a hacerle una mejora tras otra al juego...
Después de veinticuatro años, le dediqué a Alien-A varias horas de concentración y diversión, a lo largo de un mes. Fue un reencuentro muy agradable con Z80, lenguaje de programación que me gusta mucho y en el que casi no había escrito durante años.
Pantallazos
El menú de inicio puede mostrarse en tres lenguas: castellano, esperanto e inglés. Se me ocurrió que la manera más fácil de cambiar de lengua, con una sola tecla, era llamar a la opción del menú «No en X», siendo «X» la lengua actual:
Las siguientes pantallas muestran los diferentes tipos de naves que intentan aterrizar, con los rótulos en las tres lenguas:
Código fuente
; *************************************************************
; Alien-A
; A game for the Sinclair ZX Spectrum.
; Copyright (C) 1986,2010 Marcos Cruz (http://programandala.net)
; License/Licencia/Permesilo:
; http://programandala.net/license
; Alien-A is written in Z80 assembly, but it works the BASIC way:
; UDGs and character resolution movement.
; I hope Alien-A can be useful for someone learning Z80 assembly
; with the ZX Spectrum.
; Alien-A was inspired by a simpler program,
; written in Sinclair Basic and published in the ZX magazine
; (issue 1, pages 14-15, 1983):
; http://microhobby.speccy.cz/zx/revista_zx.htm
; http://microhobby.speccy.cz/zx/zx01/01-14.JPG
; http://microhobby.speccy.cz/zx/zx01/01-15.JPG
; http://microhobby.speccy.cz/zxsf/listados/progs/i/Invasores1.tzx
; *************************************************************
; History
; 1986-04-27
; * First working version.
; 1986-04-30
; * Improved with record, number of landing aliens and different aliens; no more need to press fire.
; 1986-05-04
; * Improved with stars, and new graphics inspired by Star Wars. A shield bar is shown instead of the number of landing aliens.
; 1986-06-04
; * Some bugs fixed.
; 1986-06-14
; * No bugs left. Finished.
; 2010-03-23
; * The original source, in GENS3 format, was edited in order to
; compile it with Pasmo (http://arrakis.es/~ninsesabe/pasmo/)
; on Debian GNU/Linux.
; 2010-03-24
; * Several changes in order to make the source easier to read:
; labeled ROM routines and system variables, renamed labels,
; new comments...
; * Cursor keys intead of P-O-Q-R; easier for my Dvorak keyboard layout!
; * A bit faster control key routine.
; * The aim can move diagonally.
; 2010-04-07
; * Better pseudo random numbers routine.
; 2010-04-13
; * First draft of a final effect: screen fade.
; 2010-04-14
; * Fixed: the last landing alien didn't caused the sound effect
; because the shield check was done before it.
; * The sound effects are exchanged: now aliens explode when landing.
; * Final effect: random explosions.
; * Improved: the scenery field appears quickly.
; 2010-04-15
; * Fixed: the aim flickering has been solved.
; * Final effect finished.
; * Improved: two dicker lines in the field lines.
; 2010-04-21
; * Improved: pause between the final effect and the menu, with blank screen.
; 2010-04-24
; * Improved: texts in three languages: English, Esperanto and Spanish.
; * Changed: the bar shield is printed in one single color, and it flashes when short (instead of the text).
; 2010-04-27
; * New character set, designed by Alan Grier (http://www.worldofspectrum.org/infoseekid.cgi?id=001171) in 1986, a bit modified by me.
; *************************************************************
; To do
; Check: Text positions.
; Improve: definable keys.
; Improve: don't print the "score" text every time the score changes.
; Fix: the shooted aliens not always get red. Maybe a emulator issue?
; *************************************************************
; ROM routines
CHAN_OPEN EQU #1601 ; open a channel (channel in A)
PR_STRING EQU #203C ; print a string (start in DE, count in BC)
PLOT_SUB EQU #22E5 ; the plot subroutine (coords in BC)
DRAW EQU #24BA ; point of the DRAW_LINE routine
STACK_BC EQU #2D2B ; stack BC register pair
FP_TO_BC EQU #2DA2
FP_TO_A EQU #2DD5
PRINT_FP EQU #2DE3 ; print a floating point number
; *************************************************************
; Sytem addresses
VIDEO EQU 16384
ATTRS EQU 22528
; *************************************************************
; Sytem constants
VIDEO_LENGHT EQU 6912
ATTRS_LENGHT EQU 768
BITMAP_LENGHT EQU VIDEO_LENGHT-ATTRS_LENGHT
COLUMNS EQU 32
; *************************************************************
; Sytem variables
; Absolute addresses
CHARS EQU 23606
ERR_NR EQU 23610
BORDER EQU 23624
SEED EQU 23670
FRAMES EQU 23672
UDG EQU 23675
P_FLAG EQU 23697
ATTR_P EQU 23693
ATTR_T EQU 23695
; *************************************************************
; Constants
ATTR EQU %00000111 ; white ink, black paper
TRANSPARENT EQU 8 ; keep the current attribute
OWN_CHARSET EQU 1 ; compile time flag
MAX_SHIELD EQU 32
SHIELD_ATTR EQU %01101000 ; bright, cyan paper
INK_CHR EQU 16
PAPER_CHR EQU 17
BRIGHT_CHR EQU 19
INVERSE_CHR EQU 20
OVER_CHR EQU 20
AT_CHR EQU 22
SPACE_CHR EQU 32
; *************************************************************
; Languages
LANGUAGES EQU 3 ; number of languages
EN EQU 0 ; English
EO EQU 1 ; Esperanto
ES EQU 2 ; Spanish
DEFAULT_LANGUAGE EQU EN
; *************************************************************
; System init
ENTRY ORG 32768
DI
LD A,2
CALL CHAN_OPEN
IF OWN_CHARSET
LD HL,CHAR_SET-256
LD (CHARS),HL
ENDIF
LD HL,ALIEN_UDGS
LD (UDG),HL
LD A,(FRAMES)
; OR 1 ; make sure it's not zero
LD (SEED),A
; *************************************************************
; Start
START
CALL CLS
LD DE,TITLE_TXT
LD BC,TITLE_LEN
CALL PR_STRING
PR_MENU
CALL CLEAR_MENU
LD HL,MENU_TXTS
CALL PR_LANGUAGE_STRING
LD DE,KEYS_TXT
LD BC,KEYS_LEN
CALL PR_STRING
CALL PR_LANGUAGE
FIRST_INK
LD A,1 ; blue ink
CHANGE_INK
PUSH AF ; save the ink
LD HL,ATTRS+32*3 ; from line 4
LD DE,ATTRS+32*3+1
LD BC,16*32-1 ; 16 lines
LD (HL),A
LDIR
LD BC,#0F00 ; wait counter
CHECK_KEYS
LD A,%10111111 ; keyboard semi row H-J-K-L-ENTER
IN A,(#FE)
AND %00010 ; key "L"
JR NZ,WAIT_KEY_0
RELEASE_L
LD A,%10111111 ; keyboard semi row H-J-K-L-ENTER
IN A,(#FE)
AND %00010 ; key "L"
JR Z,RELEASE_L
LD A,(LANGUAGE)
INC A
CHANGE_LANGUAGE
LD (LANGUAGE),A
CP LANGUAGES
JR C,PR_MENU
POP AF ; sync the stack
XOR A
JR CHANGE_LANGUAGE
WAIT_KEY_0
CALL KEY_0
JR NZ,CHECK_KEYS_END ; jump if "0" is not pressed
RELEASE_KEY_0
CALL KEY_0
JR Z,RELEASE_KEY_0 ; jump until "0" is not pressed
JR INIT
CHECK_KEYS_END
DEC BC
LD A,B
OR C
JR NZ,CHECK_KEYS
POP AF ; restore the ink
INC A ; next ink color
CP 8 ; no more ink colors?
JR Z,FIRST_INK ; then start again
JR CHANGE_INK
; *************************************************************
; Game init
INIT
LD HL,0
LD (SCORE),HL
LD A,MAX_SHIELD
LD (SHIELD),A
LD DE,#0A0F ; line 10, column 15
LD (AIM_COORDS),DE
CALL SCENERY
CALL OVER_1
CALL NEW_ALIEN
; *************************************************************
; Main loop
CALL PR_AIM
CALL PR_ALIEN
MAIN
CALL RANDOM
CP (IX+MOVE_PROB)
JR NC,AIM
CALL PR_ALIEN
LD DE,(ALIEN_COORDS)
CALL RANDOM
CP (IX+GLIDE_DIR)
JR C,RIGHT
; Alien
; Left
LD A,E
AND A
JR NZ,LEFT1
LD E,32
LEFT1
DEC E
AND A
JR DOWN
RIGHT
LD A,E
CP 31
JR NZ,RIGHT1
LD E,-1
RIGHT1
INC E
DOWN
LD (ALIEN_COORDS),DE
CALL RANDOM
CP (IX+DOWN_PROB)
JR NC,PR_COLOR_ALIEN
INC D
LD (ALIEN_COORDS),DE
LD A,D
CP 16 ; landing?
JR NZ,PR_COLOR_ALIEN
CALL EXPLOSION
; Decrement the shield
XOR A
CALL CHAN_OPEN
LD A,(SHIELD)
DEC A
LD (SHIELD),A
LD D,1
LD E,A
CALL AT
LD A," "
RST #10
LD A,2
CALL CHAN_OPEN
LD A,(SHIELD)
AND A
JR Z,GAME_OVER ; no shield left
CP 6
JR NZ,OTHER_ALIEN
; Almost no shield left
LD A,SHIELD_ATTR+128 ; add flash
CALL PR_SHIELD_BAR_A
OTHER_ALIEN
CALL NEW_ALIEN
PR_COLOR_ALIEN
CALL RANDOM
AND %01000111 ; keep the bright and the ink
OR 1 ; but make sure the ink is not black
LD (ATTR_T),A
CALL PR_ALIEN
LD A,ATTR
LD (ATTR_T),A
AIM
CALL KEYS
CALL FIRE
; Hold
CALL KEY_0
JR NZ,RESUME
HOLD_OFF
CALL KEY_0
JR Z,HOLD_OFF
HOLD
CALL KEY_0
JR NZ,HOLD
HOLD_OFF_2
CALL KEY_0
JR Z,HOLD_OFF_2
RESUME
LD BC,2500
DELAY
DEC BC
LD A,B
OR C
JR NZ,DELAY
JP MAIN
; *************************************************************
; Game over
GAME_OVER
LD DE,(SCORE)
LD BC,(RECORD)
LD A,B
CP D
JR C,NEW_RECORD
JR NZ,INVASION
LD A,E
CP C
JR NC,INVASION
NEW_RECORD
LD (RECORD),DE
CALL OVER_0
CALL PR_RECORD
; *************************************************************
; Invasion
INVASION
CALL OVER_1
CALL PR_AIM ; erase the aim
LD A,%00000001 ; blue ink
CALL CL_ATTR_A
CALL EXPLOSION_DELAY
CALL RANDOM
AND %00000111 ; max 7 explosions
OR %00000100 ; min 4
LD B,A
FINAL_EXPLOSION
PUSH BC
CALL EXPLOSION_DELAY
LD A,%01000111 ; bright, white ink
CALL CL_ATTR_A
CALL EXPLOSION
LD A,%00000001 ; blue ink
CALL CL_ATTR_A
POP BC
DJNZ FINAL_EXPLOSION
CALL EXPLOSION_DELAY
CALL CLS
CALL EXPLOSION_DELAY
CALL EXPLOSION_DELAY
JP START
; Random delay between explosions
EXPLOSION_DELAY
PUSH BC
CALL RANDOM
OR %0000111
LD B,A
EXPLOSION_DELAY_1
PUSH BC
LD B,8
EXPLOSION_DELAY_2
DJNZ EXPLOSION_DELAY_2
POP BC
DEC BC
LD A,B
OR C
JR NZ,EXPLOSION_DELAY_1
POP BC
RET
; *************************************************************
; Keyboard
; Is the key "0" pressed? (flag Z set if pressed)
KEY_0
LD A,%11101111 ; keyboard semi row 6-7-8-9-0
IN A,(#FE)
AND %00001 ; key "0"
RET
; Control keys
KEYS
AIM_COORDS EQU $+1
LD DE,0
LD A,%11101111 ; keyboard semi row 6-7-8-9-0
IN A,(#FE)
AND %00100 ; key "8"
JR NZ,LEFT_KEY
LD A,E
CP 30 ; right limit
JR Z,LEFT_KEY
INC E
LEFT_KEY
LD A,%11110111 ; keyboard semi row 5-4-3-2-1
IN A,(#FE)
AND %10000 ; key "5"
JR NZ,UP_KEY
LD A,E
CP 1 ; left limit
JR Z,UP_KEY
DEC E
UP_KEY
LD A,%11101111 ; keyboard semi row 6-7-8-9-0
IN A,(#FE)
AND %01000 ; key "7"
JR NZ,DOWN_KEY
LD A,D
CP 2 ; up limit
JR Z,DOWN_KEY
DEC D
DOWN_KEY
LD A,%11101111 ; keyboard semi row 6-7-8-9-0
IN A,(#FE)
AND %10000 ; key "6"
JR NZ,KEYS_END
LD A,D
CP 14 ; down limit
JR Z,KEYS_END
INC D
KEYS_END
LD HL,(AIM_COORDS)
LD A,H
CP D ; has the line changed?
JR NZ,MOVE_AIM
LD A,L
CP E ; has the colum changed?
RET Z ; return if not
; otherwise, go into MOVE_AIM and RET
; *************************************************************
; Aim
; Move the aim
; D = new line
; E = new column
MOVE_AIM
PUSH DE
CALL PR_AIM ; this erases the aim
POP DE
LD (AIM_COORDS),DE
JR PR_AIM_DE ; it's faster to jump than to load DE from memory; then RET
; Print the aim
PR_AIM
LD DE,(AIM_COORDS)
PR_AIM_DE
PUSH DE
DEC D
CALL AT
LD A,"|"
RST #10
POP DE
PUSH DE
INC D
CALL AT
LD A,"|"
RST #10
POP DE
PUSH DE
DEC E
CALL AT
LD A,"-"
RST #10
POP DE
INC E
CALL AT
LD A,"-"
RST #10
RET
; Fire
FIRE
LD DE,(ALIEN_COORDS)
LD BC,(AIM_COORDS)
LD A,D
CP B ; are the lines equal?
RET NZ
LD A,E
CP C ; are the columns equal?
RET NZ
CALL AT
LD A,%01000010 ; bright, black paper, red ink
LD (ATTR_T),A
EI
HALT
DI
LD A," "
RST #10
LD B,#FF
FIRE_1
DJNZ FIRE_1
CALL SHOOT
LD A,ATTR
LD (ATTR_T),A
LD A,8 ; backspace
RST #10
LD A,(IX+GRAPHIC)
RST #10
LD B,0
LD C,(IX+POINTS)
LD HL,(SCORE)
AND A
ADC HL,BC
LD DE,(ALIEN_COORDS)
LD E,D
LD D,0
AND A
SBC HL,DE
LD (SCORE),HL
CALL OVER_0
CALL PR_SCORE
CALL OVER_1
CALL NEW_ALIEN
JP PR_ALIEN ; and RET
; *************************************************************
; Scenery
; Print the scenery
SCENERY
CALL CLS
XOR A ; black paper, black ink
CALL CL_ATTR_A
CALL SET_ATTR_A
CALL STARS
CALL FIELD
; Prith the status line
CALL PR_SCORE
CALL PR_RECORD
CALL BRIGHT_1
CALL PR_SHIELD
CALL BRIGHT_0
; Color the sky and the field
LD A,%00000111 ; black paper, white ink
LD HL,ATTRS+32 ; from the second line
LD DE,ATTRS+32+1
LD BC,22*32-1 ; 21 lines
LD (HL),A
LDIR
if 0 ; not used any more
; Color the status line
;LD A,%01111000 ; bright, white paper, black ink
LD A,%01000111 ; bright, black paper,white ink
LD HL,ATTRS ; from the top left character
LD DE,ATTRS+1
LD BC,1*32-1 ; one line
LD (HL),A
LDIR
endif
JP SET_ATTR ; set the standard attribute and RET
; Print the stars
STARS
LD B,255 ; stars
STAR
PUSH BC
RANDOM_Y
CALL RANDOM
CP 51 ; min Y coordinate
JR C,RANDOM_Y
CP 166 ; max Y coordinate
JR NC,RANDOM_Y
PUSH AF
CALL RANDOM
LD C,A
POP AF
LD B,A
CALL PLOT_SUB
POP BC
DJNZ STAR
RET
; Print the field
FIELD
LD BC,0
CALL PLOT_SUB
LD C,97
LD B,50
LD E,1
LD D,1
CALL DRAW
LD C,255
LD B,0
CALL PLOT_SUB
LD C,97
LD B,50
LD E,255
LD D,1
CALL DRAW
LD C,137
LD B,50
CALL PLOT_SUB
LD C,50
LD B,50
LD E,1
LD D,255
CALL DRAW
LD C,117
LD B,50
CALL PLOT_SUB
LD C,50
LD B,50
LD E,255
LD D,255
CALL DRAW
LD C,127
LD B,50
CALL PLOT_SUB
LD C,0
LD B,50
LD E,1
LD D,255
CALL DRAW
LD B,50
CALL H_LINE
LD B,47
CALL H_LINE
LD B,42
CALL H_LINE
LD B,35
CALL H_LINE
LD B,24
CALL H_LINE
LD B,25
CALL H_LINE
LD B,12
CALL H_LINE
LD B,11
CALL H_LINE
LD B,10
; Draw a horizontal line
; B = Y coordinate
H_LINE
LD C,0
CALL PLOT_SUB
LD C,255
LD B,0
LD E,1
LD D,1
CALL DRAW
RET
; *************************************************************
; Screen routines
; Clear the screen
CLS
XOR A
OUT (#FE),A
LD (BORDER),A
LD HL,VIDEO
LD DE,VIDEO+1
LD BC,BITMAP_LENGHT-1
LD (HL),A
LDIR
CALL OVER_0
CALL SET_ATTR
; Set the attributes to A
CL_ATTR_A
LD HL,ATTRS
LD DE,ATTRS+1
LD BC,ATTRS_LENGHT-1
LD (HL),A
LDIR
RET
; Set the default attribute
SET_ATTR
LD A,ATTR
SET_ATTR_A
LD (ATTR_P),A
SET_ATTR_T_A
LD (ATTR_T),A
RET
; Graphic over
OVER_0
LD A,(P_FLAG)
AND %11111100
JR SET_P_FLAG
OVER_1
LD A,(P_FLAG)
OR %00000011
SET_P_FLAG
LD (P_FLAG),A
RET
if 0 ; not used
; Graphic flash
FLASH_0
LD A,(ATTR_T)
AND %01111111
JR SET_ATTR_T_A
FLASH_1
LD A,(ATTR_T)
OR %10000000
JR SET_ATTR_T_A
endif
; Graphic bright
BRIGHT_0
LD A,(ATTR_T)
AND %10111111
JR SET_ATTR_T_A
BRIGHT_1
LD A,(ATTR_T)
OR %01000000
JR SET_ATTR_T_A
; Clear the menu
CLEAR_MENU
LD D,MENU_LINE
CALL CLEAR_MENU_LINE
LD D,MENU_LINE+2
CALL CLEAR_MENU_LINE
LD D,MENU_LINE+4
CALL CLEAR_MENU_LINE
LD D,MENU_LINE+6
CALL CLEAR_MENU_LINE
LD D,MENU_LINE+9
CALL CLEAR_MENU_LINE
LD D,MENU_LINE+10
CALL CLEAR_MENU_LINE
LD D,MENU_LINE+11
CLEAR_MENU_LINE
LD E,MENU_INDENT
CALL AT
LD DE,BL_OPTION_TXT
LD BC,BL_OPTION_LEN
JP PR_STRING
; Print the record
PR_RECORD
LD DE,#000F
CALL PR_STATUS_ATTR
LD HL,RECORD_TXTS
CALL PR_LANGUAGE_STRING
RECORD EQU $+1
LD BC,0
JR PR_NUMBER
; Print the score
PR_SCORE
LD DE,#0000
CALL PR_STATUS_ATTR
LD HL,SCORE_TXTS
CALL PR_LANGUAGE_STRING
SCORE EQU $+1
LD BC,0
; Print the number in BC
PR_NUMBER
CALL STACK_BC
CALL PRINT_FP
LD A,INVERSE_CHR ; inverse...
RST #10
LD A,0 ; ...off
RST #10
LD A,BRIGHT_CHR ; bright...
RST #10
LD A,0 ; ...off
RST #10
RET
; Print the attributes of score and record
PR_STATUS_ATTR
; DE = coords
CALL AT
LD DE,STATUS_ATTR_TXT
LD BC,STATUS_ATTR_LEN
JP PR_STRING ; print the string and RET
; Print the shield
PR_SHIELD
LD A,SHIELD_ATTR
PR_SHIELD_BAR_A
LD HL,ATTRS + 32*23 ; first attribute's address of the 24th line
LD DE,ATTRS + 32*23 + 1
SHIELD EQU $+1
LD BC,MAX_SHIELD
DEC BC ; needed in order to store the shield in the former opcode, what is needed in order to preserve A and let the PR_SHIELD entry
LD (HL),A
LDIR
PR_SHIELD_TXT
XOR A
CALL CHAN_OPEN
LD A,ATTR
LD (BORDER),A
LD DE,0
CALL AT
LD HL,SHIELD_TXTS
CALL PR_LANGUAGE_STRING
LD A,2
JP CHAN_OPEN ; and RET
; Print the current language in the menu
PR_LANGUAGE
CALL AT_LANGUAGE
LD DE,BL_OPTION_TXT
LD BC,BL_OPTION_LEN
CALL PR_STRING
CALL AT_LANGUAGE
LD HL,LANGUAGE_TXTS
; Print a message depending on the language
; HL = address of the text table
PR_LANGUAGE_STRING
LANGUAGE EQU PR_LANGUAGE_STRING+1
LD A,DEFAULT_LANGUAGE
LD B,A
ADD A,B
ADD A,B ; every element in the table has 3 bytes, so A=A*3
LD B,0
LD C,A ; offset into BC
ADD HL,BC ; point to the text start
LD (TO_DE),HL
TO_DE EQU $+2
LD DE,(0)
INC HL ; point...
INC HL ; ...to the text length
LD A,(HL)
LD C,A
JP PR_STRING ; print the string and RET
; Set the cursor at the name of the language in the main menu
AT_LANGUAGE
LD DE,LANGUAGE_LINE*256+MENU_INDENT
; Set the cursor (coords in D and E)
AT
LD A,AT_CHR
RST #10
LD A,D
RST #10
LD A,E
RST #10
RET
; *************************************************************
; Alien
; New alien
NEW_ALIEN
CALL RANDOM
AND %00011111 ; mask the random column (0-31)
LD E,A
LD D,1 ; line
LD (ALIEN_COORDS),DE
CALL RANDOM
CP 64
JR NC,NEW_ALIEN_2
LD IX,ALIEN_1
RET
NEW_ALIEN_2
CP 128
JR NC,NEW_ALIEN_3
LD IX,ALIEN_2
RET
NEW_ALIEN_3
CP 192
JR NC,NEW_ALIEN_4
LD IX,ALIEN_3
RET
NEW_ALIEN_4
LD IX,ALIEN_4
RET
; Print alien
PR_ALIEN
ALIEN_COORDS EQU $+1
LD DE,0
CALL AT
LD A,(IX+GRAPHIC)
RST #10
RET
; *************************************************************
; Sound
; Landing
SHOOT
LD B,5
SHOOT_1
PUSH BC
LD HL,#0300
SHOOT_2
LD DE,1
PUSH HL
PUSH IX
CALL #03BC ; point of the BEEPER ROM routine (#03B5)
DI
POP IX
POP HL
LD DE,16
AND A
SBC HL,DE
JR NZ,SHOOT_2
POP BC
DJNZ SHOOT_1
RET
; Explosion
EXPLOSION
PUSH AF
PUSH BC
PUSH HL
LD HL,2000
LD B,0
LD E,20
EXPLOSION_1
PUSH BC
LD A,(BORDER)
SRL A
SRL A
SRL A
SET 4,A
OUT (#FE),A
LD B,(HL)
EXPLOSION_2
NOP
NOP
NOP
DJNZ EXPLOSION_2
RES 4,A
OUT (#FE),A
LD B,(HL)
EXPLOSION_3
NOP
NOP
NOP
DJNZ EXPLOSION_3
LD B,E
EXPLOSION_4
NOP
NOP
NOP
NOP
DJNZ EXPLOSION_4
INC E
INC HL
POP BC
DJNZ EXPLOSION_1
POP HL
POP BC
POP AF
RET
; *************************************************************
; Random
; Return a pseudo-random byte (0-255) in A
RANDOM
PUSH HL
PUSH BC
LD A,(SEED)
LD B,A
LD A,(FRAMES)
LD C,A
LD A,R
ADD A,B
ADD A,C
;LD HL,509 ; ROM address with the higher number of different values (166) in 256 bytes
LD HL,13990 ; ROM address pointing to 256 misc values; somehow its result is better
LD B,0
LD C,A
ADC HL,BC
LD A,(HL)
LD (SEED),A
POP BC
POP HL
RET
; *************************************************************
; User Defined Graphics
ALIEN_UDGS
DEFB %00100001
DEFB %01100011
DEFB %11101011
DEFB %11110111
DEFB %11111111
DEFB %11101011
DEFB %01100011
DEFB %00100001
DEFB %01000010
DEFB %10000001
DEFB %10011001
DEFB %11100111
DEFB %10111101
DEFB %10011001
DEFB %10000001
DEFB %01000010
DEFB %10000100
DEFB %11000110
DEFB %11010111
DEFB %11101111
DEFB %11111111
DEFB %11010111
DEFB %11000110
DEFB %10000100
; *************************************************************
; Alien's data
; Field offsets
GRAPHIC EQU 0 ; alien's UDG number
GLIDE_DIR EQU 1 ; glide direction degree: 0 (left)...center (127)...rigth (255)
DOWN_PROB EQU 2 ; probability of the alien going down (0...255) (landing speed)
MOVE_PROB EQU 3 ; probability of the alien moving (0...255) (general activity)
POINTS EQU 4 ; points got when the alien is destroyed
; Data
ALIEN_1 DEFB 146 ; UDG
DEFB 0 ; left gliding
DEFB 55 ; landing speed
DEFB 50 ; move probability
DEFB 100 ; points
ALIEN_2 DEFB 145 ; UDG
DEFB 127 ; vertical gliding
DEFB 250 ; landing speed
DEFB 50 ; move probability
DEFB 200 ; points
ALIEN_3 DEFB 145 ; UDG
DEFB 127 ; vertical gliding
DEFB 20 ; landing speed
DEFB 200 ; move probability
DEFB 200 ; points
ALIEN_4 DEFB 144 ; UDG
DEFB 255 ; right gliding
DEFB 55 ; landing speed
DEFB 50 ; move probability
DEFB 100 ; points
; *************************************************************
; Texts
LANGUAGE_LINE EQU 17
LANGUAGE_TXTS DEFW LANGUAGE_EN_TXT
DEFB LANGUAGE_EN_LEN
DEFW LANGUAGE_EO_TXT
DEFB LANGUAGE_EO_LEN
DEFW LANGUAGE_ES_TXT
DEFB LANGUAGE_ES_LEN
LANGUAGE_EN_TXT DEFM "Not in English"
LANGUAGE_EN_LEN EQU $-LANGUAGE_EN_TXT
LANGUAGE_EO_TXT DEFM "Ne en Esperanto"
LANGUAGE_EO_LEN EQU $-LANGUAGE_EO_TXT
LANGUAGE_ES_TXT DEFM "No en castellano"
LANGUAGE_ES_LEN EQU $-LANGUAGE_ES_TXT
BL_OPTION_TXT DEFM " "
BL_OPTION_LEN EQU $-BL_OPTION_TXT
STATUS_ATTR_TXT
DEFB PAPER_CHR,0
DEFB INK_CHR,7
DEFB BRIGHT_CHR,1
STATUS_ATTR_LEN EQU $-STATUS_ATTR_TXT
SCORE_TXTS DEFW SCORE_EN_TXT
DEFB SCORE_EN_LEN
DEFW SCORE_EO_TXT
DEFB SCORE_EO_LEN
DEFW SCORE_ES_TXT
DEFB SCORE_ES_LEN
SCORE_EN_TXT DEFM "Score "
SCORE_EN_LEN EQU $-SCORE_EN_TXT
SCORE_EO_TXT DEFM "Poentoj "
SCORE_EO_LEN EQU $-SCORE_EO_TXT
SCORE_ES_TXT DEFM "Puntos "
SCORE_ES_LEN EQU $-SCORE_ES_TXT
RECORD_TXTS DEFW RECORD_EN_TXT
DEFB RECORD_EN_LEN
DEFW RECORD_EO_TXT
DEFB RECORD_EO_LEN
DEFW RECORD_ES_TXT
DEFB RECORD_ES_LEN
RECORD_EN_TXT DEFM "Record "
RECORD_EN_LEN EQU $-RECORD_EN_TXT
RECORD_EO_TXT DEFM "Rikordo "
RECORD_EO_LEN EQU $-RECORD_EO_TXT
RECORD_ES_TXT DEFM "Marca "
RECORD_ES_LEN EQU $-RECORD_ES_TXT
SHIELD_TXTS DEFW SHIELD_EN_TXT
DEFB SHIELD_EN_LEN
DEFW SHIELD_EO_TXT
DEFB SHIELD_EO_LEN
DEFW SHIELD_ES_TXT
DEFB SHIELD_ES_LEN
SHIELD_EN_TXT DEFM "Shield:"
SHIELD_EN_LEN EQU $-SHIELD_EN_TXT
SHIELD_EO_TXT DEFB 96
DEFM "irmilo:"
SHIELD_EO_LEN EQU $-SHIELD_EO_TXT
SHIELD_ES_TXT DEFM "Escudo:"
SHIELD_ES_LEN EQU $-SHIELD_ES_TXT
KEYS_INDENT EQU 7
KEYS_TXT DEFB AT_CHR,MENU_LINE,KEYS_INDENT
DEFM "5"
DEFB AT_CHR,MENU_LINE+2,KEYS_INDENT
DEFM "6"
DEFB AT_CHR,MENU_LINE+4,KEYS_INDENT
DEFM "7"
DEFB AT_CHR,MENU_LINE+6,KEYS_INDENT
DEFM "8"
DEFB AT_CHR,MENU_LINE+9,KEYS_INDENT
DEFM "0"
DEFB AT_CHR,LANGUAGE_LINE,KEYS_INDENT
DEFM "L"
KEYS_LEN EQU $-KEYS_TXT
MENU_TXTS DEFW MENU_EN_TXT
DEFB MENU_EN_LEN
DEFW MENU_EO_TXT
DEFB MENU_EO_LEN
DEFW MENU_ES_TXT
DEFB MENU_ES_LEN
MENU_LINE EQU 4
MENU_INDENT EQU 10
MENU_EN_TXT DEFB AT_CHR,MENU_LINE,MENU_INDENT
DEFM "Left"
DEFB AT_CHR,MENU_LINE+2,MENU_INDENT
DEFM "Down"
DEFB AT_CHR,MENU_LINE+4,MENU_INDENT
DEFM "Up"
DEFB AT_CHR,MENU_LINE+6,MENU_INDENT
DEFM "Right"
DEFB AT_CHR,MENU_LINE+9,MENU_INDENT
DEFM "Play/"
DEFB AT_CHR,MENU_LINE+10,MENU_INDENT
DEFM "Halt/"
DEFB AT_CHR,MENU_LINE+11,MENU_INDENT
DEFM "Continue"
MENU_EN_LEN EQU $-MENU_EN_TXT
MENU_EO_TXT DEFB AT_CHR,MENU_LINE,MENU_INDENT
DEFM "Maldekstre"
DEFB AT_CHR,MENU_LINE+2,MENU_INDENT
DEFM "Malsupre"
DEFB AT_CHR,MENU_LINE+4,MENU_INDENT
DEFM "Supre"
DEFB AT_CHR,MENU_LINE+6,MENU_INDENT
DEFM "Dekstre"
DEFB AT_CHR,MENU_LINE+9,MENU_INDENT
DEFM "Ludi/"
DEFB AT_CHR,MENU_LINE+10,MENU_INDENT
DEFM "Haltigi/"
DEFB AT_CHR,MENU_LINE+11,MENU_INDENT
DEFM "Pluigi"
MENU_EO_LEN EQU $-MENU_EO_TXT
MENU_ES_TXT DEFB AT_CHR,MENU_LINE,MENU_INDENT
DEFM "Izquierda"
DEFB AT_CHR,MENU_LINE+2,MENU_INDENT
DEFM "Abajo"
DEFB AT_CHR,MENU_LINE+4,MENU_INDENT
DEFM "Arriba"
DEFB AT_CHR,MENU_LINE+6,MENU_INDENT
DEFM "Derecha"
DEFB AT_CHR,MENU_LINE+9,MENU_INDENT
DEFM "Jugar/"
DEFB AT_CHR,MENU_LINE+10,MENU_INDENT
DEFM "Detener/"
DEFB AT_CHR,MENU_LINE+11,MENU_INDENT
DEFM "Continuar"
MENU_ES_LEN EQU $-MENU_ES_TXT
TITLE_TXT DEFB AT_CHR,0,5
DEFB BRIGHT_CHR,1
DEFM "A L I E N - A"
DEFB AT_CHR,20,4
DEFB 127 ; copyright character
DEFM " 1986, 2010 Marcos Cruz"
DEFB AT_CHR,21,4
DEFM "http://programandala.net"
DEFB BRIGHT_CHR,0
TITLE_LEN EQU $-TITLE_TXT
; *************************************************************
; Character set
IF OWN_CHARSET
CHAR_SET INCBIN alien-a_charset.bin
ENDIF
; *************************************************************
END ENTRY ; set the entry point
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