; GAME 3 - Fly Escape ; by Krzysztof Krystian Jankowski ^ P1X ; ; Version 1.0 - 18 MAY 2024 ; Version 1.1 - 19 MAY 2024 ; Version 2.0 - 25 MAY 2024 ; Version 2.1 - 26 MAY 2024 bits 16 ; 16-bit mode org 0x7c00 ; Boot sector origin cpu 286 ; Minimum CPU is Intel 286 ; =========================================== MEMORY =========================== VGA_MEMORY_ADR equ 0xA000 ; VGA memory address DBUFFER_MEMORY_ADR equ 0x1000 ; Doublebuffer memory address SCREEN_BUFFER_SIZE equ 0xFA00 ; Size of the VGA buffer size TIMER equ 0x046C ; BIOS timer BASE_MEM equ 0x7e00 ; Base memory address LIFE equ BASE_MEM+0x00 ; Number of lifes, 1 byte LEVEL equ BASE_MEM+0x01 ; Current level, 2 bytes SPRITE equ BASE_MEM+0x03 ; Current sprite, 2 bytes COLOR equ BASE_MEM+0x05 ; Current color, 1 byte PLAYER equ BASE_MEM+0x06 ; Player data, 5 bytes of: ; sprite ID, 1 byte ; color, 1 byte ; rotation, 1 byte ; position, 2 bytes ENTITIES equ BASE_MEM+0x0B ; 5 bytes per entitie ; =========================================== MAGIC NUMBERS ==================== SCREEN_WIDTH equ 320 ; 320x200 pixels SCREEN_HEIGHT equ 200 SCREEN_CENTER equ SCREEN_WIDTH*SCREEN_HEIGHT/2+SCREEN_WIDTH/2 ; Center SPRITE_SIZE equ 8 ; 8 pixels per sprite line SPRITE_LINES equ 7 ; 7 lines per sprite MAX_ENTITIES equ 128 ; Maximum number of entities ENEMIES_PER_LEVEL equ 4 ; Number of enemies per level COLOR_BG equ 20 ; Background color COLOR_SPIDER equ 0 ; Spider color COLOR_FLOWER equ 10 ; Flower color COLOR_FLY equ 77 ; Fly color SPRITE_FLY equ 0 ; Fly sprite ID (position in memory) SPRITE_SPIDER equ 14 ; Spider sprite ID SPRITE_FLOWER equ 28 ; Flower sprite ID ; =========================================== BOOTSTRAP ======================== _start: xor ax, ax ; Clear AX mov ds, ax ; Set DS to 0 mov ax, 0x13 ; Init VGA 320x200x256 int 0x10 ; Video BIOS interrupt push DBUFFER_MEMORY_ADR ; Set doublebuffer memory pop es ; as target ; =========================================== GAME INITIALIZATION / RESET ====== restart_game: mov byte [LIFE], 0x04 ; Starting lifes mov word [LEVEL], 0x00 ; Starting level mov word [PLAYER+1], (0x06 << 8) | COLOR_FLY ; Set player color and sprite mov si, ENTITIES ; Set memory position to entites mov cx, MAX_ENTITIES ; Number of enemies .clear_entites: mov byte [si], 0 ; Clear sprite ID add si, 5 ; Move to next memory position loop .clear_entites ; Loop for all enemies ; =========================================== LEVEL INITIALIZATION / NEXT LEVEL next_level: mov word [PLAYER+3], SCREEN_CENTER ; Set player initial position inc word [LEVEL] ; 0 -> 1st level mov si, ENTITIES ; Set memory position to entites mov bx, [LEVEL] ; Current level number imul cx, bx, ENEMIES_PER_LEVEL ; Multiply enemies by level number .next_entitie: cmp cx, 1 ; Check counter ja .spawn_spider ; Spawn spider on all others .spawn_flower: ; Spawn flower on first entitie mov word [si], (COLOR_FLOWER << 8) | SPRITE_FLOWER ; Set sprite ID and color for flower jmp .spawn_done .spawn_spider: mov word [si], (COLOR_SPIDER << 8) | SPRITE_SPIDER ; Set sprite ID and color for spider .spawn_done: mov byte al, [TIMER] ; Get random number add ax, si ; Add memory position and ax, SCREEN_BUFFER_SIZE ; Clip screen size mov word [si+3], ax ; Set position add ax, si ; Add memory position and al, 7 ; Clip rotation mov byte [si+2], al ; Set direction add si, 5 ; Move to next memory position loop .next_entitie ; Repeat for all enemies ; =========================================== MAIN GAME LOOP =================== game_loop: ; =========================================== DRAW BACKGROUND ================== draw_bg: xor di,di ; Clear DI xor bx,bx ; Clear BX mov bx, [LEVEL] ; Get current level number imul ax, bx, 0x0404 ; Multiply level by 0x0404 add ax, 0xa0a0 ; Shift colors by 10 mov dx, 8 ; We have 8 bars .draw_bars: mov cx, 320*200/16 ; One bar of 320x200 rep stosw ; Write to the doublebuffer inc ax ; Increment color index for next bar xchg al, ah ; Swap colors dec dx ; Decrement bar counter jnz .draw_bars ; Repeat for all bars ; =========================================== DRAW LEVEL ======================= xor di, di ; Clear DI - top left corner mov al, 0x0f ; Set color to 15 mov cl, bl rep stosw ; Write to the doublebuffer ; 2x pixels per level ; =========================================== DRAW ENTITIES ==================== draw_entities: mov cx, MAX_ENTITIES ; Number of enemies to check mov si, ENTITIES ; Start index for positions .next: push cx ; Save counter push si ; Save position xor ax,ax ; Clear AX mov byte al, [si] ; Sprite frame cmp al, 0 ; Check if it's not empty je .skip_this_one ; Skip if empty mov word [SPRITE], ax ; Set sprite frame mov ax, [TIMER] ; Get timer value and al, 2 ; Limit to 0..1 jnz .ok ; If 1, add frame add word [SPRITE], 7 ; Move to the second sprite frame .ok: mov byte al, [si+1] ; Get color mov byte [COLOR], al ; Set color mov di, [SI+3] ; Get position .move_player_and_enemies: cmp byte [SPRITE], SPRITE_SPIDER; Check if it's a spider ja .draw_entitie ; Do not move if not a spider .move_entitie_forward: xor ax,ax ; Clear AX mov al, [si+2] ; Direction mov si, ax ; Set SI to direction shl si, 1 ; Shift left add di, [MLT + si] ; Movement Lookup Table cmp di, SCREEN_BUFFER_SIZE ; Check if out of bounds jb .draw_entitie ; No clip below and di, SCREEN_BUFFER_SIZE ; Clip screen size .draw_entitie: push di ; Save position mov byte BL, [COLOR] ; Set color mov si, sprites ; Set sprites data position add word si, [SPRITE] ; Shift to the current sprite call draw_sprite ; Draw the sprite pop di ; Restore position .skip_this_one: ; Jump to here to pop si, cx ; wihtout additional code pop si ; Restore position mov word [si+3], di ; Save new, updated position .random_rotate: mov ax, [TIMER] ; Get timer value add ax, di ; Add position and ax, 66 ; Wait until 66 jg .skip mov byte al, [TIMER] ; Get random number add ax, si ; Add memory position and al, 7 ; Clip rotation 0..7 mov byte [si+2], al ; Save direction .skip: add si, 5 ; Move to the next entitie data pop cx loop .next ; =========================================== COLLISION CHECKING =============== check_collisions: mov di, [PLAYER+3] ; Get player position mov bx, SPRITE_LINES ; Number of rows to check .check_row: mov cx, 8 ; Number of columns to check mov si, di ; Set SI to player position .check_column: mov al, [es:si] ; Get pixel color at player position cmp al, COLOR_SPIDER ; Check if it matches spider color je .collision_spider ; Jump if collision with spider cmp al, COLOR_FLOWER ; Check if it matches flower color je .collision_flower ; Jump if collision with flower inc si ; Move to the next column loop .check_column add di, 320 ; Move to the next row dec bx ; Decrement row counter jnz .check_row jmp .collision_done ; No collision .collision_flower: jmp next_level ; Advance to the next level .collision_spider: mov word [PLAYER+3], SCREEN_CENTER ; Reset player position dec byte [LIFE] ; Decrease life jnz .collision_done ; If lifes left, continue .waint_for_esc: ; If no lifes left, wait for ESC in al, 60h ; Read keyboard cmp al, 0x01 ; Check if ESC key is pressed jne .waint_for_esc jmp restart_game .collision_done: ; =========================================== PLAYER MOVEMENT ================== handle_player: mov di, [PLAYER+3] ; Position mov byte bl, [PLAYER+1] ; Color mov byte al, [PLAYER+2] ; Rotation mov ah, 0 ; Clear AH mov si, ax ; Set SI to rotation shl si, 1 ; Shift left add di, [MLT + si] ; Movement Lookup Table add di, [MLT + si] ; Second time for faster movement mov word [PLAYER+3], DI ; Save new position mov si, sprites+SPRITE_FLY ; Sprite mov byte al, [TIMER] ; Get random number and al, 2 ; Last bit jnz .ok ; If 1, add frame add si, 7 ; Move to the second srite frame .ok: call draw_sprite ; Draw player sprite ; =========================================== DRAW LIFES ======================= mov byte cl, [LIFE] ; Set lifes sub di, 320*9 ; Move to the top mov ax, 0x040c ; Set color to red and light red rep stosw ; Write to the doublebuffer ; 2x pixels per life ; =========================================== KEYBOARD INPUT =================== handle_keyboard: in al, 60h ; Read keyboard cmp al, 0x39 ; Check if Spacebar is pressed jne .no_rotate inc byte [PLAYER+2] ; Move rotation clockvise and byte [PLAYER+2], 7 ; Limit 0..7 .no_rotate: ; =========================================== VGA BLIT ========================= vga_blit: push es push ds push VGA_MEMORY_ADR ; Set VGA memory pop es ; as target push DBUFFER_MEMORY_ADR ; Set doublebuffer memory pop ds ; as source mov cx, 0x7D00 ; Half of 320x200 pixels xor si, si ; Clear SI xor di, di ; Clear DI rep movsw ; Push words (2x pixels) pop ds pop es ; =========================================== DELAY CYCLE ====================== %ifdef IS_286 %else delay_timer: mov ax, [TIMER] ; Get current timer value inc ax ; Increment it by 1 cycle (42ms) .wait: cmp [TIMER], ax ; Compare with the current timer jl .wait ; Loop until equal %endif ; =========================================== END OF GAME LOOP ================= jmp game_loop ; Repeat the game loop ; =========================================== DRAWING SPRITE PROCEDURE ========= draw_sprite: mov dx, SPRITE_LINES ; Number of lines in the sprite .draw_row: mov al, [si] ; Get sprite row data mov cx, 8 ; 8 bits per row .draw_pixel: shl al, 1 ; Shift left to get the pixel out jnc .skip_pixel ; If carry flag is 0, skip mov [es:di], bl ; Carry flag is 1, set the pixel .skip_pixel: inc di ; Move to the next pixel position loop .draw_pixel ; Repeat for all 8 pixels in the row inc si add di, 312 ; Move to the next line dec dx ; Decrement row count jnz .draw_row ; Draw the next row ret ; =========================================== DATA ============================= MLT dw -320,-319,1,321,320,319,-1,-321 ; Movement Lookup Table sprites: db 0x60, 0x96, 0x49, 0x32, 0x5C, 0x7D, 0x1E ; Fly sprite frame 0 db 0x00, 0x00, 0x1E, 0x72, 0x5C, 0x7D, 0x1E ; Frame 1 db 0x06, 0x77, 0xAF, 0xFE, 0x2A, 0x49, 0x49 ; Spider sprite frame 0 db 0x06, 0x77, 0xAF, 0xFE, 0x2B, 0xD4, 0x14 ; Frame 1 db 0x1C, 0x36, 0x1C, 0x48, 0x3F, 0x08, 0x08 ; Flower sprite frame 0 db 0x38, 0x6C, 0x38, 0x09, 0x7E, 0x08, 0x08 ; Frame 1 ; =========================================== BOOTSECTOR ======================= times 507 - ($ - $$) db 0 ; Pad remaining bytes db 'P1X' ; P1X signature 3b dw 0xAA55 ; Boot signature