; Example 14: A Poor Excuse of a Game. Nothing new has been used! include int_start.i ; Initialise the BitMap structure Main lea MyBitMap,a0 a0->BitMap struct move.l #1,d0 Depth move.l #320,d1 Width move.l #256,d2 height CALLGRAF InitBitMap initialise structure ; Link bitplane memory into BitMap structure lea MyBitMap,a0 a0->BitMap lea bm_Planes(a0),a0 a0->bm_Planes field lea bitplanes,a1 a1->start of mem block ; Write first bitplane start address into structure move.l a1,(a0) write bitplane addr ; Link BitMap structure to NewScreen structure lea MyScreen,a0 a0->NewScreen move.l #MyBitMap,ns_CustomBitMap(a0) link BitMap ; Set screens type move.w #CUSTOMBITMAP!CUSTOMSCREEN,ns_Type(a0) ; Open the Custom Screen lea MyScreen,a0 NewScreen struct CALLINT OpenScreen open it move.l d0,screen.ptr save pointer beq error quit if error ; Set scroll counter and collision flag move.l #5,ScrollCount init counter move.l #0,HitFlag clear flag ; Wait for mouse press MWait btst #2,$dff016 beq AllDone ; Check for collision tst.l HitFlag bne AllDone exit if set ; Wait for vertical blanking period CALLGRAF WaitTOF ; Update counter subq.l #1,ScrollCount dec counter bne.s NoPlot ; Plot next asteroid and reset counter bsr RND get random position bsr PlotAsteroid plot asteroid move.l #5,ScrollCount reset counter ; Scroll display down a line NoPlot lea bitplanes,a0 bitplane to scroll bsr ScrollDown scroll it ; Plot the ship bsr MoveShip check movements move.l ShipX,d0 x pixel position bsr PlotShip plot the ship ; And loop back bra MWait loop ; Freeze screen for player to see collision AllDone bsr LeftMouse ; Close the screen move.l screen.ptr,a0 a0->screen struct CALLINT CloseScreen close it error rts and exit ;-------------- Scroll Down ; scroll screen down 1 line ; Entry a0->start of bitplane memory ; Exit Nothing special ; corrupt a0-a2,d0 ScrollDown adda.l #(320/8)*249,a0 1st long past bitplane move.l a0,a1 suba.l #40,a1 1st long. last line move.l #2369,d0 number of longs ; The scroll loop .loop move.l -(a1),-(a0) copy long word dbra d0,.loop for whole display ; And exit rts exit ;-------------- Plot an asteroid ; Entry d0=x byte position PlotAsteroid lea bitplanes+440,a0 a0->top line free add.l d0,a0 a0->addr to plot at lea Asteroid,a1 a1->data move.b (a1)+,(a0) copy 1st line lea 40(a0),a0 a0->next addr move.b (a1)+,(a0) copy 2nd line lea 40(a0),a0 a0->next addr move.b (a1)+,(a0) copy 3rd line lea 40(a0),a0 a0->next addr move.b (a1)+,(a0) copy 4th line lea 40(a0),a0 a0->next addr move.b (a1)+,(a0) copy 5th line lea 40(a0),a0 a0->next addr move.b (a1)+,(a0) copy 6th line rts ;-------------- Plot The Ship ; Entry d0=x pixel position ; Corrupt a0,a1,d0,d1 PlotShip lea bitplanes+249*40,a0 a0->Ships top line divu #16,d0 swap d0 move.w d0,d1 d1=bit scroll move.w #0,d0 swap d0 asl.l #1,d0 force even add.l d0,a0 a0->addr to plot at lea Ship,a1 a1->data ; Check for collision move.l -40(a0),d0 get data above ship asl.l d1,d0 correct and.l #$f0000000,d0 test bits beq.s .DoPlot skip if no collision move.l #-1,HitFlag signal collision .DoPlot move.l (a1)+,d0 get line of data asr.l d1,d0 scroll it move.l d0,(a0) and draw this line lea 40(a0),a0 a0->next scrn addr move.l (a1)+,d0 get line of data asr.l d1,d0 scroll it move.l d0,(a0) and draw this line lea 40(a0),a0 a0->next scrn addr move.l (a1)+,d0 get line of data asr.l d1,d0 scroll it move.l d0,(a0) and draw this line lea 40(a0),a0 a0->next scrn addr move.l (a1)+,d0 get line of data asr.l d1,d0 scroll it move.l d0,(a0) and draw this line lea 40(a0),a0 a0->next scrn addr move.l (a1)+,d0 get line of data asr.l d1,d0 scroll it move.l d0,(a0) and draw this line lea 40(a0),a0 a0->next scrn addr move.l (a1)+,d0 get line of data asr.l d1,d0 scroll it move.l d0,(a0) and draw this line lea 40(a0),a0 a0->next scrn addr rts ;-------------- Generate a random number in range 1->specified number<65535 ; Entry None ; Exit d0=random number between 1 and 39 ; Corrupt d0,d1 RND moveq.l #39,d0 max value, <65535! move.l d0,d1 move.l d1,-(sp) move.l a0,-(sp) move.l Seed,d0 get seed rol.l d0,d0 scramble bits move.l d0,d1 and.l #$7fffe,d1 create random ptr into CHIP move.l d1,a0 add.l (a0),d0 add onto scrambled bits add.l d0,Seed save value move.l (sp)+,a0 move.l (sp)+,d1 and.l #$ffff,d0 mulu d1,d0 divu #$ffff,d0 and.l #$ffff,d0 rts ;-------------- Check for ship movement MoveShip bsr TestJoy get joystick data btst #0,d2 check right beq.s .CheckLeft skip if not ; moving right, check is legal and update if so! move.l ShipX,d0 x coordinate cmp.l #310,d0 at right edge? beq.s .DoneMoving exit if so! addq.l #1,d0 update move.l d0,ShipX save bra.s .DoneMoving and exit! ; See if moving left, exit if not! .CheckLeft btst #1,d2 check left beq.s .DoneMoving exit if not move.l ShipX,d0 x coordinate beq.s .DoneMoving exit if 0 subq.l #1,d0 update move.l d0,ShipX and save ; Done moving, so exit! .DoneMoving rts ;-------------- Read the joystick ; Subroutine to read joystick movement in port 1. Returns a code in register ;d2 according to the following: ; bit 0 set = right movement ; bit 1 set = left movement ; bit 2 set = down movemwnt ; bit 3 set = up movement ; Assumes a5 -> hardware registers ( ie a5 = $dff000 ). ; Corrupts a5, d0, d1 and d2. ; M.Meany, Aug 91. JOY1DAT equ $00c TestJoy lea $dff000,a5 a5->hardware reg moveq.l #0,d0 clear move.l d0,d2 move.w JOY1DAT(a5),d0 read stick btst #1,d0 right ? beq.s .test_left if not jump! or.w #1,d2 set right bit .test_left btst #9,d0 left ? beq.s .test_updown if not jump or.w #2,d2 set left bit .test_updown move.l d0,d1 copy JOY1DAT lsr.w #1,d1 shift u/d bits eor.w d1,d0 exclusive or 'em btst #0,d0 down ? beq.s .test_down if not jump or.w #4,d2 set down bit .test_down btst #8,d0 up ? beq.s .no_joy if not jump or.w #8,d2 set up bit .no_joy rts ; Static Intuition structures and variables MyBitMap ds.b bm_SIZEOF space for BitMap structure MyScreen dc.w 0,0 ;screen XY origin relative to View dc.w 320,256 ;screen width and height dc.w 1 ;screen depth (number of bitplanes) dc.b 1,0 ;detail and block pens dc.w 0 ;display modes for this screen dc.w 0 ;screen type dc.l 0 ;pointer to default screen font dc.l .Title ;pointer to screen title dc.l 0 ;first in list of custom screen gadgets dc.l 0 ;pointer to custom BitMap structure .Title dc.b ' This is fun???',0 even screen.ptr dc.l 0 ShipX dc.l 100 HitFlag dc.l 0 Seed dc.l 15 ScrollCount dc.l 0 ; CHIP MEM section for graphics! Asteroid dc.b %00000000 dc.b %01011010 dc.b %00111100 dc.b %01111110 dc.b %00111100 dc.b %01011010 even Ship dc.b %01111110,0,0,0 dc.b %01000010,0,0,0 dc.b %00100100,0,0,0 dc.b %00100100,0,0,0 dc.b %00011000,0,0,0 dc.b %00011000,0,0,0 ; BSS CHIP MEM section for bitplane memory section gfx,BSS_C bitplanes ds.b (320/8)*256 ds.b 200 safety margin!