; ---------------------------------------------------------------------- ; MINIMAL - Minimal game for Ludum Dare 26. ; Programmed by MegaBrutal, 28 April 2013. ; Post-compo update, V1.0, 11 June 2013. ; ; Compile with NASM: ; nasm -o minimal.com minimal.asm ; ; The output is a DOS .COM file which you may run with NTVDM, DOSEmu, ; DOSBox, or... you know, under actual DOS. ;) ; ; Also, this program can be booted directly from a storage media (such ; as a floppy, most typically). To do this, you need to write the ; binary into the media's first sectors. ; ; For example, to make a bootable floppy under DOS/Windows, use the ; popular RAWRITE utility (several implementations exist, Google to ; find a suitable one). ; ; Under Linux, use the GNU DD utility, e.g.: ; dd if=minimal.com of=/dev/fd0 bs=512 ; (Might require root privileges.) ; ---------------------------------------------------------------------- ORG 100h ; Preserve space for Program Segment Prefix. CLI ; Disable hardware interrupts CLD ; Clear direction flag, just in case ; Check if direct-booted from a floppy (or other media). ; BIOS loads boot record at 0000:7C00. MOV AX, CS CMP AX, 0 JNE DOSCODE_START ; If running under DOS, skip boot code ; ---------------------------------------------------------------------- ; BOOT CODE ; ; Executes if program is loaded upon boot sequence, otherwise it's ; jumped over. This code sets up a small DOS-like environment for the ; game to allow it to run flawlessly. Anything essential for this ; process needs to be located within the first 512 bytes of the binary ; file, since BIOS will only load the first sector from the media upon ; boot. ; ; ; MEMORY MAP: ; 07B0:0000 - Dummy PSP start (of course we don't really have a PSP now, still preserve the space) ; 07B0:0100 - Start of boot record ; 07B0:0300 - Read buffer (load rest of code here) ; ---------------------------------------------------------------------- ; Fix code location to be 100h based. ; Physical address: 07C00h - 100h = 07B00h -> Start of 100h based code: 07B0:0100. JMP 07B0h:LOCATION_FIXED LOCATION_FIXED: ; HACK: Copy the INT 19h interrupt vector to the INT 20h vector, ; so when the game quits with INT 20h (that would return control ; to DOS under DOS), it'll actually call INT 19h which instructs ; BIOS to restart the boot sequence... Wicked, huh? :D XOR AX, AX MOV DS, AX MOV ES, AX MOV SI, 19h * 4 MOV DI, 20h * 4 MOVSW ; Loading CX and using the REP prefix would take more bytes, MOVSW ; so I just write it down twice. ;) ; (And no, I won't use MOVSD, that's only supported since 80386! ; I can't expect everyone to have cutting edge technology! :p) ; Set up segment registers and stack MOV AX, CS MOV DS, AX MOV ES, AX MOV SS, AX MOV SP, 0FFFEh STI ; Re-enable hardware interrupts READ_TRY: ; Since only the first 512 bytes are currently loaded (that is contained in the boot record), ; we need to load the next 2 sectors from the media. MOV AX, 0202h ; AH = 02h means read from disk; AL tells how many sectors MOV CX, 2 ; Read from Sector #2; Cylinder 0 XOR DH, DH ; Head 0 ; Assuming drive number was stored in DL by BIOS upon boot MOV BX, 300h ; (ES:BX) Data buffer to load rest of code (see memory map above) INT 13h ; Try to read (INT 13h/AH=02h: ) JNC DOSCODE_START XOR AX, AX INT 13h ; Reset drive before next read attempt DEC BYTE [BIOSFAIL] JNZ READ_TRY ; EPIC FAIL - couldn't load rest of program, show a friendly message and reboot. MOV DH, 24 MOV DL, 0 MOV SI, STR_FAIL CALL PRINT_STRING CALL READ_KEY INT 19h DOSCODE_START: JMP START DD 0DEADDEADh ; Easter Egg for Omni DB 0Dh, 0Ah DB "Minimal game for Ludum Dare 26.", 0Dh, 0Ah DB "Programmed by MegaBrutal, 28 April 2013.", 0Dh, 0Ah DB "Post-compo update, V1.0, 11 June 2013.", 0Dh, 0Ah, 00h STR_FAIL DB "Failed to load game! ", 00h ; Yes, those spaces are necessary, trust me! BIOSFAIL DB 10 ; Maximum number of INT 13h read retry attempts ; Some cute subroutines ; ---------------------------------------------------------------------- ; SCREEN_CLREOLN: Clear to end of line from given cursor position. ; Inputs: ; DH - cursor position - row ; DL - cursor position - column ; ; Outputs: ; None. ; ---------------------------------------------------------------------- SCREEN_CLREOLN: PUSH ES PUSH DI PUSH AX PUSH BX PUSH DX MOV AX, 0B800h ; Video memory starts at B800:0000 MOV ES, AX XOR AX, AX MOV AL, DH MOV BX, 80 * 2 MUL BX ; Calculate row POP DX MOV DI, AX MOV BL, DL ; BH is cleared by above MOV BX, 80 * 2 SHL BX, 1 ADD DI, BX ; Add column position MOV CX, 80 SUB CL, DL ; # of characters to end of line MOV AX, 0720h ; 07h = Light gray; 20h = Space REP STOSW POP BX POP AX POP DI POP ES RET ; ---------------------------------------------------------------------- ; PRINT_CHAR: Prints character at location. ; Inputs: ; AL - character to print ; DH - row ; DL - column ; ; Outputs: ; None. ; ---------------------------------------------------------------------- PRINT_CHAR: PUSHF PUSH BX PUSH CX PUSH AX MOV AH, 02h XOR BX, BX INT 10h ; Row & column are already set by caller (DX). POP AX PUSH AX ; To preserve AH. MOV AH, 09h MOV BL, 07h ; Light gray. MOV CX, 1 INT 10h ; Put character POP AX POP CX POP BX POPF RET ; ---------------------------------------------------------------------- ; PRINT_STRING: Prints a zero-terminated string. ; Inputs: ; DH - row ; DL - column ; SI - address of string ; ; Outputs: ; DL - new column position of the cursor ; SI - end of the printed string ; ---------------------------------------------------------------------- PRINT_STRING: PUSH AX PS_LOOP: LODSB CMP AL, 0 JE PS_EXIT CALL PRINT_CHAR ; DH, DL are already set up INC DL JMP PS_LOOP PS_EXIT: POP AX RET ; ---------------------------------------------------------------------- ; READ_KEY: Reads a key from the keyboard. (Wrapper, in case I'll change ; the read method. - Currently it's INT 16h/00h.) ; Inputs: ; None. ; ; Outputs: ; AH - BIOS scan code ; AL - ASCII character ; ---------------------------------------------------------------------- READ_KEY: XOR AX, AX INT 16h RET ; ---------------------------------------------------------------------- ; SCREEN_CLEAR: Clear screen. ; Inputs: ; None. ; ; Outputs: ; None. ; ---------------------------------------------------------------------- SCREEN_CLEAR: PUSH ES PUSH DI PUSH AX PUSH CX MOV AX, 0B800h MOV ES, AX XOR DI, DI MOV AX, 0720h ; Light gray spaces everywhere MOV CX, 80 * 25 REP STOSW POP CX POP AX POP DI POP ES RET ; ---------------------------------------------------------------------- ; PRINT_NUMBER: Prints a number to the screen in decimal, right-aligned, ; fixed field size. ; Inputs: ; AX - number to print ; CX - field size ; DH - row ; DL - column (of least significant digit of the number) ; ; Outputs: ; DL - column right before the last printed digit ; ---------------------------------------------------------------------- PRINT_NUMBER: PUSH AX PUSH BX PUSH CX PUSH DX PRINTN: MOV BX, 10 XOR DX, DX DIV BX ; Save quotient in BX, move remainder to AX MOV BX, AX MOV AX, DX ADD AL, '0' ; Convert remainder to ASCII character POP DX ; Restore column/row CALL PRINT_CHAR MOV AX, BX ; Restore quotient to AX DEC DL ; Decrement column (next digit will be printed there) PUSH DX ; Save column/row for the next division LOOP PRINTN ; Print next digit unless CX = 0 POP DX POP CX POP BX POP AX RET ; ---------------------------------------------------------------------- ; BOOT RECORD SIGNATURE ; ; A valid boot record must contain the word 0AA55h (little-endian) in ; the last 2 bytes of the sector (offset 01FEh), otherwise BIOS would ; refuse to boot from the media. ; ---------------------------------------------------------------------- TIMES 01FEh-$+$$ DB 0 ; Align to 01FEh by padding space with zeros DW 0AA55h ; ---------------------------------------------------------------------- ; GAME DATA & CODE ; ; Actual game code and data are located in the 2nd and 3rd sectors. ; ---------------------------------------------------------------------- ; Some cute constants %DEFINE MAX_HEALTH 200 %DEFINE PLAYERCHR 'O' %DEFINE POTIONCHR '*' %DEFINE MONSTERCHR '@' %DEFINE KEY_UP 48h %DEFINE KEY_DOWN 50h %DEFINE KEY_RIGHT 4Bh %DEFINE KEY_LEFT 4Dh %DEFINE OBJECT_POTION 01h %DEFINE OBJECT_TREASURE 02h %DEFINE OBJECT_MONSTER 03h %DEFINE STRPOS_HEALTH 1 %DEFINE STRPOS_TREASURES 14 %DEFINE STRPOS_KILLS 30 %DEFINE STRPOS_STATUS 42 %DEFINE STRPOSN_HEALTH STRPOS_HEALTH + 8+2 %DEFINE STRPOSN_TREASURES STRPOS_TREASURES + 11+2 %DEFINE STRPOSN_KILLS STRPOS_KILLS + 7+2 ; Some cute variables RANDSEED DW 0 PLAYER_POS DW 0 HEALTH DW MAX_HEALTH / 2 TREASURES DW 0 KILLS DW 0 ; Some cute strings (zero terminated) STR_HEALTH DB "Health:", 00h STR_TREASURES DB "Treasures:", 00h STR_KILLS DB "Kills:", 00h STR_KILLED DB "You killed", 00h STR_DEAD DB "You were killed by", 00h STR_POTION DB "You drank a potion.", 00h STR_TRFOUND DB "You found a treasure.", 00h ; Various enemy names STR_DEMON DB "a demon", 00h STR_DRAGON DB "a dragon", 00h STR_GOBLIN DB "a goblin", 00h STR_WILDBOAR DB "a wild boar", 00h STR_WIZARD DB "a wizard", 00h STR_OGRE DB "an ogre", 00h STR_ZOMBIE DB "a zombie", 00h STR_SUCCUBUS DB "a succubus", 00h STR_SERAPH DB "a seraph", 00h STR_PEGASUS DB "a dark pegasus", 00h STR_MANTICORE DB "a manticore", 00h STR_CHIMAERA DB "a chimaera", 00h STR_MIMIGA DB "an enraged mimiga", 00h ; Hurray Cave Story! STR_LEEBLE DB "a leeble", 00h ; Hello Shigi! STR_MVYR DB "a m'vyr", 00h ; How's the Ghost Shards demo progressing, Strawberry? :P STR_GOOBALL DB "a goo ball", 00h ; I had the Best of Times with World of Goo! STR_HEXAGON DB "a super hexagon", 00h ; Terry's Hexagonest Hardestestest Super Hexagon! \o/ STR_HELLHOUND DB "a hellhound", 00h ; No one will get this, but I thought of Reincarnation: Dawn of War! STR_FURDIBURB DB "a furdiburb", 00h ; Small's Furdiburb game for Android! ARRAY_ENEMIES DW STR_DEMON, STR_DRAGON, STR_GOBLIN, STR_WILDBOAR, STR_WIZARD, STR_OGRE, STR_ZOMBIE DW STR_SUCCUBUS, STR_SERAPH, STR_PEGASUS, STR_MANTICORE, STR_CHIMAERA DW STR_MIMIGA, STR_LEEBLE, STR_MVYR, STR_GOOBALL, STR_HEXAGON, STR_HELLHOUND, STR_FURDIBURB ARRAYL_ENEMIES EQU ($-ARRAY_ENEMIES) / 2 ; Some even cuter subroutines ; ---------------------------------------------------------------------- ; RANDOM_CORE: Linear congruential pseudorandom number generator (LCG). ; Inputs: ; None. ; ; Outputs: ; AX - next random number ; ---------------------------------------------------------------------- %DEFINE RAND_A 5 ; LCG parameter 'a' %DEFINE RAND_C 64539 ; LCG parameter 'c' RANDOM_CORE: PUSH DX MOV AX, RAND_A MUL WORD [RANDSEED] ; a * r ADD AX, RAND_C ; + c MOV [RANDSEED], AX ; Store new seed. POP DX RET ; ---------------------------------------------------------------------- ; RANDOM_INIT: Initializes LCG with a seed obtained from the system ; clock. ; Inputs: ; None. ; ; Outputs: ; None. ; ---------------------------------------------------------------------- RANDOM_INIT: PUSH AX PUSH CX PUSH DX XOR AX, AX INT 1Ah ; Get system time - tick count will be stored in CX:DX; MOV [RANDSEED], DX ; only use lower 16 bits for seed. POP DX POP CX POP AX RET ; ---------------------------------------------------------------------- ; RANDOM: Gets a random number between the specified boundaries using ; the above defined RANDOM_CORE function. ; Inputs: ; AX - modulus ; BX - offset ; ; Outputs: ; AX - result ; ---------------------------------------------------------------------- RANDOM: PUSH CX PUSH DX XOR DX, DX MOV CX, AX ; Save modulus to CX. CALL RANDOM_CORE ; Get next pseudorandom number in AX. DIV CX ; Divide AX with CX. MOV AX, DX ; Store remainder of division. ADD AX, BX ; Add offset. POP DX POP CX RET ; ---------------------------------------------------------------------- ; FIX_PLAYER_POSITION: If player went out of screen, warp him to the ; other side. (Maybe the messiest function in the entire program. :p) ; Inputs: ; BX - address of player position ; ; Outputs: ; [BX] - fixed player position ; ---------------------------------------------------------------------- FIX_PLAYER_POSITION: PUSH AX MOV AX, [BX] CMP AL, 80 JE FPP_WARP_RIGHT CMP AL, -1 JE FPP_WARP_LEFT JMP FPP_CONT FPP_WARP_RIGHT: XOR AL, AL JMP FPP_EXIT FPP_WARP_LEFT: MOV AL, 79 JMP FPP_EXIT FPP_CONT: CMP AH, 24 JE FPP_WARP_DOWN CMP AH, -1 JE FPP_WARP_UP JMP FPP_EXIT FPP_WARP_DOWN: XOR AH, AH JMP FPP_EXIT FPP_WARP_UP: MOV AH, 23 FPP_EXIT: MOV [BX], AX POP AX RET ; ---------------------------------------------------------------------- ; GAME_INIT: Initialize game data. ; Inputs: ; None. ; ; Outputs: ; None. ; ---------------------------------------------------------------------- GAME_INIT: PUSH AX PUSH BX PUSH CX PUSH DI ; XOR AX, AX ; MOV DI, GAMEDATA ; MOV CX, 80 * 24 / 2 ; REP STOSW ; Fill space with zeros. ; Put some stuff on the field. ; (Intended to be random but I don't have time - sorry. :P) ; (Hey, but I used random.org to choose these, really!) ; LEA BX, [GAMEDATA] ; MOV [BX + 78 + (80 * 20)], BYTE OBJECT_POTION ; MOV [BX + 37 + (80 * 13)], BYTE OBJECT_POTION ; MOV [BX + 71 + (80 * 5)], BYTE OBJECT_POTION ; MOV [BX + 40 + (80 * 3)], BYTE OBJECT_POTION ; MOV [BX + 63 + (80 * 19)], BYTE OBJECT_POTION ; MOV [BX + 56 + (80 * 19)], BYTE OBJECT_POTION ; MOV [BX + 57 + (80 * 0)], BYTE OBJECT_POTION ; MOV [BX + 27 + (80 * 1)], BYTE OBJECT_POTION ; MOV [BX + 50 + (80 * 1)], BYTE OBJECT_TREASURE ; MOV [BX + 3 + (80 * 18)], BYTE OBJECT_TREASURE ; MOV [BX + 2 + (80 * 23)], BYTE OBJECT_TREASURE ; MOV [BX + 50 + (80 * 15)], BYTE OBJECT_TREASURE ; MOV [BX + 33 + (80 * 15)], BYTE OBJECT_TREASURE ; MOV [BX + 44 + (80 * 24)], BYTE OBJECT_TREASURE ; MOV [BX + 64 + (80 * 19)], BYTE OBJECT_TREASURE ; MOV [BX + 28 + (80 * 9)], BYTE OBJECT_TREASURE ; MOV [BX + 38 + (80 * 13)], BYTE OBJECT_MONSTER ; MOV [BX + 1 + (80 * 7)], BYTE OBJECT_MONSTER ; MOV [BX + 70 + (80 * 3)], BYTE OBJECT_MONSTER ; MOV [BX + 6 + (80 * 18)], BYTE OBJECT_MONSTER ; MOV [BX + 53 + (80 * 20)], BYTE OBJECT_MONSTER ; MOV [BX + 77 + (80 * 22)], BYTE OBJECT_MONSTER ; MOV [BX + 16 + (80 * 13)], BYTE OBJECT_MONSTER ; MOV [BX + 22 + (80 * 23)], BYTE OBJECT_MONSTER ; Now that the above shit has been commented out, ; time for some real random field generation. ;) MOV DI, GAMEDATA MOV CX, 80 * 24 GI_LOOP: MOV AX, 20 XOR BX, BX CALL RANDOM CMP AX, 0 ; 1/20 possibility of spawning an item/monster JE GI_SPAWN_OBJECT XOR AL, AL JMP GI_LOOP_END GI_SPAWN_OBJECT: MOV AX, OBJECT_MONSTER MOV BX, 1 CALL RANDOM GI_LOOP_END: STOSB LOOP GI_LOOP POP DI POP CX POP BX POP AX RET ; ---------------------------------------------------------------------- ; GAME_DRAW: Draws initial game field. ; Inputs: ; None. ; ; Outputs: ; None. ; ---------------------------------------------------------------------- GAME_DRAW: PUSH AX PUSH CX PUSH DX PUSH SI XOR DX, DX LEA SI, [GAMEDATA] MOV CX, 24 GD_BIGLOOP: PUSH CX MOV CX, 80 GD_SMALLLOOP: LODSB ; Load next byte from GAMEDATA... CMP AL, 0 ; ...determine what it is... JE GD_NOTOBJECT CMP AL, OBJECT_MONSTER JNE GD_NOTMONSTER MOV AL, MONSTERCHR JMP GD_CONT GD_NOTMONSTER: MOV AL, POTIONCHR GD_CONT: CALL PRINT_CHAR ; ...print appropriate character. GD_NOTOBJECT: INC DL LOOP GD_SMALLLOOP XOR DL, DL INC DH POP CX LOOP GD_BIGLOOP ; Write stats MOV DH, 24 MOV DL, STRPOS_HEALTH LEA SI, [STR_HEALTH] CALL PRINT_STRING MOV DL, STRPOS_TREASURES LEA SI, [STR_TREASURES] CALL PRINT_STRING MOV DL, STRPOS_KILLS LEA SI, [STR_KILLS] CALL PRINT_STRING POP SI POP DX POP CX POP AX RET ; ---------------------------------------------------------------------- ; GAME_PRINT_STATS: Print player stats (health, treasures, kills). ; This only prints the numbers, not the captions. ; Inputs: ; None. ; ; Outputs: ; None. ; ---------------------------------------------------------------------- GAME_PRINT_STATS: PUSH AX PUSH CX PUSH DX MOV AX, WORD [HEALTH] MOV CX, 3 MOV DH, 24 MOV DL, STRPOSN_HEALTH CALL PRINT_NUMBER MOV AX, WORD [TREASURES] ; MOV CX, 4 MOV DL, STRPOSN_TREASURES CALL PRINT_NUMBER MOV AX, WORD [KILLS] ; MOV CX, 4 MOV DL, STRPOSN_KILLS CALL PRINT_NUMBER POP DX POP CX POP AX RET ; ---------------------------------------------------------------------- ; GAME_PRINT_STATUS: Prints a status message. ; Inputs: ; SI - address of string to print as status ; ; Outputs: ; DH - 24 ; DL - actual column position of cursor ; ---------------------------------------------------------------------- GAME_PRINT_STATUS: PUSH SI MOV DH, 24 MOV DL, STRPOS_STATUS CALL SCREEN_CLREOLN CALL PRINT_STRING ; SI is already loaded by caller. POP SI RET ; ---------------------------------------------------------------------- ; GAME_PRINT_STATUS_ENEMY: Prints a compound message involving a ; randomly selected enemy. ; Inputs: ; SI - address of status string ; ; Outputs: ; None. ; ---------------------------------------------------------------------- GAME_PRINT_STATUS_ENEMY: PUSH AX PUSH BX PUSH DX PUSH SI CALL GAME_PRINT_STATUS ; MOV AL, 20h ; Space. ; CALL PRINT_CHAR INC DL ; Move one character. (PRINT_CHAR doesn't adjust DL accordingly.) MOV AX, ARRAYL_ENEMIES XOR BX, BX CALL RANDOM SHL AX, 1 ; Shift left by 1 bit effectively multiplies by 2. MOV BX, AX ; Move to BX, since AX can't be used in effective address calculation. MOV SI, [ARRAY_ENEMIES + BX] CALL PRINT_STRING MOV AL, "!" CALL PRINT_CHAR POP SI POP DX POP BX POP AX RET ; ---------------------------------------------------------------------- ; GAME_HANDLE_BATTLE: Prints that the player has killed a random enemy. ; Inputs: ; None. ; ; Outputs: ; None. ; ---------------------------------------------------------------------- GAME_HANDLE_BATTLE: PUSH SI MOV SI, STR_KILLED CALL GAME_PRINT_STATUS_ENEMY POP SI RET ; ---------------------------------------------------------------------- ; GAME_HANDLE_DEAD: Prints player death message. ; Inputs: ; None. ; ; Outputs: ; None. ; ---------------------------------------------------------------------- GAME_HANDLE_DEAD: PUSH AX PUSH SI MOV [HEALTH], WORD 0 ; Health is supposedly negative, correct to 0. CALL GAME_PRINT_STATS ; Update stats, one last time. MOV SI, STR_DEAD CALL GAME_PRINT_STATUS_ENEMY CALL READ_KEY ; Wait for a keypress before exiting. POP SI POP AX RET ; ---------------------------------------------------------------------- ; GAME_LOOP: Run game. ; Inputs: ; None. ; ; Outputs: ; Garbage (doesn't preserve registers). ; ---------------------------------------------------------------------- GAME_LOOP: CALL GAME_PRINT_STATS MOV DX, [PLAYER_POS] ; Player position will be stored in DX. GL_ENTER: MOV AL, PLAYERCHR CALL PRINT_CHAR ; Print player - DX is already set. CALL READ_KEY PUSH AX MOV AL, 20h ; Space. CALL PRINT_CHAR ; Clear previous player position. POP AX CMP AH, KEY_UP JE GL_PLAYERUP CMP AH, KEY_DOWN JE GL_PLAYERDOWN CMP AH, KEY_RIGHT JE GL_PLAYERRIGHT CMP AH, KEY_LEFT JE GL_PLAYERLEFT CMP AX, 011Bh ; ESC? JE GL_EXIT JMP GL_ENTER GL_PLAYERUP: DEC DH JMP GL_CONT GL_PLAYERDOWN: INC DH JMP GL_CONT GL_PLAYERRIGHT: DEC DL JMP GL_CONT GL_PLAYERLEFT: INC DL GL_CONT: MOV [PLAYER_POS], DX MOV BX, PLAYER_POS CALL FIX_PLAYER_POSITION JC GL_NOTWARPED ; Check if warped. CALL SCREEN_CLEAR CALL GAME_INIT ; Generate new field. CALL GAME_DRAW ; Draw new field. GL_NOTWARPED: XOR AX, AX ; Calculate GAMEDATA pos based on player pos. MOV AL, DH MOV BX, 80 MUL BL XOR DH, DH ADD AX, DX LEA SI, [GAMEDATA] MOV BX, AX MOV AL, [SI + BX] CMP AL, OBJECT_MONSTER JE GL_BATTLE CMP AL, OBJECT_POTION JE GL_POTION CMP AL, OBJECT_TREASURE JE GL_TREASURE JMP GAME_LOOP GL_BATTLE: PUSH BX ; Honestly not sure if BX needs to be preserved... MOV AX, 25 MOV BX, 5 CALL RANDOM ; (Min. 5, max 30 points of damage.) POP BX ; ...still did it just in case. SUB [HEALTH], AX JBE GL_DEAD ; Check if player is dead. INC WORD [KILLS] CALL GAME_HANDLE_BATTLE JMP GL_CLEARITEM GL_POTION: ADD [HEALTH], WORD 5 CMP [HEALTH], WORD MAX_HEALTH JNA GL_P_NA MOV [HEALTH], WORD MAX_HEALTH ; Cap health at MAX_HEALTH GL_P_NA: PUSH DX PUSH SI MOV SI, STR_POTION CALL GAME_PRINT_STATUS POP SI POP DX JMP GL_CLEARITEM GL_TREASURE: INC WORD [TREASURES] PUSH DX PUSH SI MOV SI, STR_TRFOUND CALL GAME_PRINT_STATUS POP SI POP DX GL_CLEARITEM: MOV [SI + BX], BYTE 0 ; Remove object so player won't encounter it again. JMP GAME_LOOP GL_DEAD: CALL GAME_HANDLE_DEAD GL_EXIT: ; Set cursor to the bottom of the screen. MOV AH, 02h XOR BX, BX MOV DH, 25 INT 10h RET START: MOV AX, 0003h INT 10h ; Set 80x25 color text mode. CALL RANDOM_INIT CALL SCREEN_CLEAR CALL GAME_INIT CALL GAME_DRAW CALL GAME_LOOP INT 20h ; Return to DOS. GAMEDATA: TIMES 0600h-$+$$ DB 0 ; Pad file to exact 3 sectors length.