***************************************************************************** * * * Amiga system takeover framework * * 1988 Dave Jones, DMA Design * * * * Allows killing of system, allowing changing of all display & blitter * * hardware, restoring to normal after exiting. * * Memory must still be properly allocated/deallocated upon entry/exit * * DOS routines for loading must be called BEFORE killing the system * * * * Written using Devpac2 * * * ***************************************************************************** section Framework,code_c incdir "fast:devpac/include/" include libraries/dos_lib.i include exec/exec_lib.i include hardware/custom.i Hardware equ $dff000 SystemCopper1 equ $26 SystemCopper2 equ $32 PortA equ $bfe001 ICRA equ $bfed01 LeftMouse equ 6 BackgroundWidth equ 100 100 bytes wide ForegroundWidth equ 92 92 bytes wide ScreenHeight equ 192 playing area 192 lines high (12 blocks) NumberPlanes equ 3 3 planes in each playfield BytesPerBackPlane equ BackgroundWidth*ScreenHeight BytesPerForePlane equ ForegroundWidth*ScreenHeight BackgroundMemory equ 2*NumberPlanes*BytesPerBackPlane ForegroundMemory equ NumberPlanes*BytesPerForePlane MemNeeded equ BackgroundMemory+ForegroundMemory FullFirepower equ 0 aliensize equ 24<<6!3 firedelay equ 3 ******************************************************************************* start lea GraphicsName(pc),a1 open the graphics library purely move.l _SysBase,a6 to find the system copper clr.l d0 jsr _LVOOpenLibrary(a6) move.l d0,GraphicsBase lea DOSName(pc),a1 open the DOS library to allow clr.l d0 the loading of data before jsr _LVOOpenLibrary(a6) killing the system move.l d0,DOSBase move.l #MemNeeded,d0 properly allocate some chip moveq.l #2,d1 memory for screens etc. jsr _LVOAllocMem(a6) d1 = 2, specifies chip memory tst.l d0 where screens,samples etc beq MemError must be (bottom 512K) move.l d0,MemBase ******************************************************************************* lea variables(pc),a5 a5 is the variables pointer lea rasters(a5),a0 lea displayraster(a5),a1 move.l d0,(a0)+ calculate the address of each plane move.l d0,(a1)+ store them in the variables area, add.l #BytesPerBackPlane,d0 twice for the background as it is move.l d0,(a0)+ double buffered move.l d0,(a1)+ add.l #BytesPerBackPlane,d0 move.l d0,(a0)+ move.l d0,(a1)+ add.l #BytesPerBackPlane,d0 move.l d0,(a0)+ add.l #BytesPerForePlane,d0 move.l d0,(a0)+ add.l #BytesPerForePlane,d0 move.l d0,(a0)+ add.l #BytesPerForePlane,d0 move.l d0,(a0)+ move.l d0,(a1)+ add.l #BytesPerBackPlane,d0 move.l d0,(a0)+ move.l d0,(a1)+ add.l #BytesPerBackPlane,d0 move.l d0,(a0)+ move.l d0,(a1)+ move.l #Hardware,a6 jsr TakeSystem ******************************************************************************* move.l #$dff000,a6 a6 ALWAYS point to base of move.l #-1,bltafwm(a6) custom chips bsr GameInit move.l #clist,cop1lc(a6) move.w #$87e0,dmacon(a6) enable copper,sprite,blitter move.w #$7fff,intreq(a6) clear all int request flags move.w #$0c30,clxcon(a6) ******************************************************************************* * Main game loop with the routines we are yet to cover commented out ******************************************************************************* vloop bsr waitline223 interrupt set at vertical not.b vcount(a5) position 223 (panel start) beq twoblanks alternate every frame lea copperlist(pc),a1 set up registers for routine move.w pf2scroll(a5),d0 checkpf2 move.w pf1scroll(a5),d1 bsr checkpf2 and branch to it bsr moveship bsr check.collision bsr erase.missiles bsr levels.code bsr update.missiles bsr drawfgnds * bsr print.score * bsr check.keys bsr check.path bra vloop twoblanks bsr checkpf1 the following routines are only bsr flipbgnd executed every second frame bsr moveship bsr restorebgnds restore backgrounds behind aliens bsr process.aliens bsr save.aliens save the backgrounds behind aliens bsr draw.aliens and then draw the aliens tst.b kill.game(a5) beq vloop bra alldone ************************************************************************** waitline223 btst #4,intreqr+1(a6) wait for vertical line 223 beq waitline223 interrupt set by the move.w #$10,intreq(a6) copperlist return rts ************************************************************************** checkpf1 cmp.w #3,level.end(a5) level.end = 3 means beq return guardian on, so no scroll lea copperlist(pc),a1 move.w pf2scroll(a5),d0 d0 = pf2 scroll value (0-15) move.w pf1scroll(a5),d1 d1 = pf1 scroll value (0-15) subq.w #1,d1 scroll a pixel bcs resetpf1 reset back to 15 checkpf2 cmp.w #3,level.end(a5) as above beq return subq.w #1,d0 scroll a pixel bcs resetpf2 reset to 15 and update pointers storescroll move.w d1,pf1scroll(a5) resave the values move.w d0,pf2scroll(a5) move.w pf1count(a5),d2 subq.w #1,d2 check if at the end of the two or.w d1,d2 screens and flag for the sprite move.w d2,screenend(a5) routine if true lsl.w #4,d0 or.w d0,d1 move.w d1,54(a1) put the new scroll value into rts the copper list resetpf1 moveq #$f,d1 reset scroll to 15 subq.w #1,pf1count(a5) decrement words scrolled bne storepf1 carry on if not zero move.w #23,pf1count(a5) otherwise reset the number of lea rasters(a5),a4 words to scroll and reset the lea displayraster(a5),a3 display planes back to the very move.l (a4)+,(a3)+ start. move.l (a4)+,(a3)+ move.l (a4)+,(a3)+ six planes in all add.w #12,a4 move.l (a4)+,(a3)+ move.l (a4)+,(a3)+ move.l (a4)+,(a3)+ bra checkpf2 now check pf2 storepf1 lea displayraster(a5),a3 increment the plane pointers addq.l #2,(a3) by a word each addq.l #2,4(a3) these are background planes addq.l #2,8(a3) and are therefore double addq.l #2,12(a3) buffered addq.l #2,16(a3) addq.l #2,20(a3) bra checkpf2 resetpf2 lea rasters(a5),a4 moveq #$f,d0 reset scroll back to 15 subq.w #1,pf2count(a5) decrement the word scroll bne respf2 value and reset if zero move.w #23,pf2count(a5) clr.w pf2offset(a5) offset is reverse of pf2count cmp.w #1,level.end(a5) and is used for the copper bne respf2 level.end = 1 when map finished addq.w #1,level.end(a5) so start to draw guardian bsr change.colours setup the guardian colours move.w #6*72,guard.offset(a5) changes the missiles respf2 move.l 12(a4),d2 get the foreground plane move.l 16(a4),d3 pointers and add the offset to move.l 20(a4),d4 them addq.w #2,pf2offset(a5) add.w pf2offset(a5),d2 store these in the copper list add.w pf2offset(a5),d3 add.w pf2offset(a5),d4 storepf2 move.w d2,30(a1) move.w d3,38(a1) move.w d4,46(a1) bra storescroll ************************************************************************** flipbgnd lea copperlist(pc),a1 swap the background displays lea displayraster(a5),a3 every second frame move.l (a3),d4 move.l 4(a3),d5 move.l 8(a3),d6 move.l 12(a3),(a3) move.l 16(a3),4(a3) move.l 20(a3),8(a3) move.l d4,12(a3) move.l d5,16(a3) move.l d6,20(a3) addq #4,d4 add 4 bytes (32 pixels) to the addq #4,d5 pointers so that clipping can addq #4,d6 be carried out on the left move.w d4,6(a1) hand side swap d4 move.w d4,2(a1) store the new ones in the copper move.w d5,14(a1) list swap d5 move.w d5,10(a1) move.w d6,22(a1) swap d6 move.w d6,18(a1) not.b screen.num(a5) rts ************************************************************************** drawfgnds cmp.w #3,level.end(a5) 3 for guardian fully on beq return cmp.w #2,level.end(a5) 2 for drawing guardian beq draw.guardian tst.w pf2scroll(a5) every 16 pixels a new strip beq drawbegin of foreground graphics are cmp.w #$e,pf2scroll(a5) drawn into a hidden part beq drawend of the screen rts drawbegin bsr setupblit clr.l d6 d6 = offset into the screen move.l fgndpointer(a5),a0 for the start of the screen bsr drawfgnd this will be zero subq #1,a0 move.l a0,fgndpointer(a5) rts drawend bsr setupblit moveq #46,d6 as the screen is 46 bytes move.l fgndpointer(a5),a0 wide, this is the offset cmp.b #$ff,(a0) at which to draw the strip bne drawfgnd sub.w #12,a0 the end of map is flagged move.l a0,fgndpointer(a5) by an FF block number move.w #1,level.end(a5) flag the end of the map drawfgnd clr.l d0 move.b (a0)+,d0 d0 = block number (0-254) lea rasters(a5),a4 get the current foreground move.l 12(a4),d1 plane pointers in d1,d2,d3 move.l 16(a4),d2 move.l 20(a4),d3 add.l d6,d1 add the offset passed add.l d6,d2 add.l d6,d3 add.w pf2offset(a5),d1 add the scrolled words add.w pf2offset(a5),d2 offset to each plane add.w pf2offset(a5),d3 moveq #11,d7 12 blocks in height move.l #graphics,a4 a4 = base address of the graphics fgndloop move.l a4,d4 mulu #96,d0 96 bytes per graphic blocks ext.l d0 (2 bytes wide x 16 high add.l d0,d4 x 3 planes) bsr blitfgnd add.l #ForegroundWidth*16,d1 work out address of 16 scanlines add.l #ForegroundWidth*16,d2 down add.l #ForegroundWidth*16,d3 clr.l d0 move.b (a0)+,d0 get next block number dbf d7,fgndloop and repeat for all 12 rts blitfgnd move.l d1,bltdpt(a6) blit a 16x16 pixel block move.l d4,bltapt(a6) into the foreground screen move.w #$0401,bltsize(a6) unmasked with no shift add.l #32,d4 move.l d2,bltdpt(a6) move.l d4,bltapt(a6) move.w #$0401,bltsize(a6) add.l #32,d4 move.l d3,bltdpt(a6) move.l d4,bltapt(a6) move.w #$0401,bltsize(a6) rts setupblit move.w #$09f0,bltcon0(a6) minterm for D = A clr.w bltcon1(a6) clr.w bltamod(a6) data is stored sequentially move.w #ForegroundWidth-2,bltdmod(a6) rts ************************************************************************** buildbackgnd lea rasters(a5),a0 move.l (a0),a1 get the background plane pointers move.l 4(a0),a2 in a1-a4 (double buffered so 2 sets) move.l 24(a0),a3 background graphics are only 4 colour move.l 28(a0),a4 (2 planes) so third plane is ignored addq #4,a1 skip the hidden words used for addq #4,a2 clipping addq #4,a3 addq #4,a4 move.l #backgroundtable,a0 a0 = the background map move.w level.number(a5),d0 mulu #144,d0 144 bytes per background map add.w d0,a0 moveq #11,d0 12 blocks high build1 moveq #11,d1 24 blocks across movem.l a1-a4,-(sp) build2 move.b (a0),d2 this loop draws 2 across lsr.b #4,d2 block number stored in 4 bits bsr drawback move.b (a0)+,d2 and.b #$f,d2 tst.w d1 beq skipit bsr drawback skipit dbf d1,build2 do all 24 across movem.l (sp)+,a1-a4 add.l #BackgroundWidth*16,a1 next block down the way add.l #BackgroundWidth*16,a2 add.l #BackgroundWidth*16,a3 add.l #BackgroundWidth*16,a4 dbf d0,build1 do all 12 high move.l #$dff000,a6 rts drawback lea backgrounds,a6 a6 = the background graphics move.w level.number(a5),d3 mulu #1024,d3 1024 bytes per level of background add.w d3,a6 graphics (16 blocks) and.w #$f,d2 mulu #64,d2 64 bytes per block add.l d2,a6 (2 bytes x 16 high x 2 planes) movem.l a1-a4,-(sp) moveq #15,d3 drawb1 move.w (a6),(a1) draw into both the screens move.w (a6),(a3) move.w (a6),46(a1) move.w (a6),46(a3) move.w 32(a6),(a2) move.w 32(a6),(a4) move.w 32(a6),46(a4) move.w 32(a6),46(a2) add.w #BackgroundWidth,a1 add.w #BackgroundWidth,a2 add.w #BackgroundWidth,a3 add.w #BackgroundWidth,a4 addq #2,a6 dbf d3,drawb1 movem.l (sp)+,a1-a4 addq #2,a1 next block along addq #2,a2 addq #2,a3 addq #2,a4 rts ************************************************************************** GameInit lea map,a0 move.l a0,fgndpointer(a5) set up the map index move.w #23,pf1count(a5) width of the foreground in words move.w #24,pf2count(a5) width of the background in words move.w #15,pf1scroll(a5) initial scroll value move.w #15,pf2scroll(a5) move.w #100,xpos(A5) ships initial x,y & speed move.w #80,ypos(a5) move.w #2,ship.speed(a5) move.w #1,mult.number(a5) move.l #ship1.2,shipaddress(a5) setup address of initial ship move.w #10,path.delay(a5) move.w #5,bonus.count(a5) move.w #128,ship.energy(a5) move.w #$ffff,ship.count(a5) move.w #324-12,d0 bsr max.energy move.l #explosion.sequence,explosion.ptr(a5) move.l #guardian+384,guardian.data(a5) move.w #999,guardian.count(a5) lea copperlist(pc),a1 lea rasters(a5),a0 move.w (a0),2(a1) copy the plane adresses into the move.w 2(a0),6(a1) copperlist move.w 4(a0),10(a1) move.w 6(a0),14(a1) move.w 8(a0),18(a1) move.w 10(a0),22(a1) move.w 12(a0),26(a1) move.w 14(a0),30(a1) move.w 16(a0),34(a1) move.w 18(a0),38(a1) move.w 20(a0),42(a1) move.w 22(a0),46(a1) addq.w #4,6(a1) skip the hidden words in the addq.w #4,14(a1) background addq.w #4,22(a1) lea scroll.value(pc),a0 move.w #$ff,2(a0) move.l #panel+32,d0 put the address of the panel lea rastersplit2(pc),a1 graphics into the copper moveq #3,d1 the panel is 4 planes setup1 move.w d0,6(a1) swap d0 move.w d0,2(a1) swap d0 add.l #1408,d0 panel size is 352x32 (1408 bytes addq #8,a1 per plane) dbf d1,setup1 lea level.colours(pc),a0 copy the level colours into the lea colours(pc),a1 copperlist moveq #31,d0 .copy move.w (a0)+,2(a1) addq #4,a1 dbf d0,.copy lea panel.colours(pc),a0 copy the panel colours into the lea colours2(pc),a1 copperlist moveq #15,d0 .copy2 move.w (a0)+,2(a1) addq #4,a1 dbf d0,.copy2 bsr ship.to.copper setup the hardware sprite pointers bsr clear.screen bsr buildbackgnd and draw the background bsr setup.mouse IFNE FullFirepower st.b mult1.on(a5) st.b mult2.on(a5) st.b canons.on(a5) st.b lasers.on(A5) move.w #2,ship.speed(A5) move.b #3,ship.status(a5) bsr change.ship ENDC rts clear.screen move.l rasters(a5),a0 clear all the screen memory move.w #MemNeeded/4-1,d0 clear.scr1 clr.l (a0)+ dbf d0,clear.scr1 rts ************************************************************************** check.collision tst.b ship.dead(a5) no action taken if he's dead bne return move.w clxdat(a6),d0 get collison value in d0 bsr collect.bonus check if bonus mode and.w #$46,d0 beq return no collision, so return tst.w field.count(a5) is force field on bne return cmp.b #3,last.path(a5) is guardian dead beq return move.w ship.count(a5),d2 and.w #$6,d0 bits 1 & 2 of clxdat for background beq check3 tst.b last.path(a5) beq normal.value decrease by 8 if guardian path normal.value lsr.w #5,d2 bcc shield.decrease no.decrease move.w d2,ship.count(a5) rts check3 cmp.w #2,level.end(a5) bge foreground.hit guardian always deadly tst.w difficulty(a5) beq return no effect on easy level foreground.hit lsr.w #3,d2 on level. This is less than for bcs no.decrease alien collisons shield.decrease subq.w #2,ship.energy(a5) bit 5 of clxdat for foreground move.w ship.energy(a5),d1 bmi explode if shield <0 start the explosion move.w #$ffff,ship.count(a5) reset secondary count move.w #324-12,d0 bra decrease.energy explode st ship.dead(a5) flag ship dead move.w xpos(a5),d4 move.w ypos(a5),d5 clr.l d0 return longword in do add.w #44,d5 hardware offset vertical lsl.w #8,d5 into bits 8-15 add.w #128,d4 horizontal offset lsr.w #1,d4 /2 low bit into extend or.w d5,d4 X intact move.w d4,d0 X still intact swap d0 ditto roxl.w #1,d0 get low bit of hstart into bit 0 add.w #$1800,d5 calcualate vstop (+24 lines) or.w d5,d0 low word set up move.l d0,d1 move.l d0,d2 add.l #$00080000,d1 3 sprites for the explosion add.l #$00100000,d2 so each is 16 pixels apart lea ship.explosion,a1 moveq #9,d7 setup.sprite move.l d0,(a1) store the new coords in the ten move.l d1,104(a1) explosion animations move.l d2,208(a1) add.l #312,a1 dbf d7,setup.sprite lea colours(pc),a0 move.w #$fd0,70(a0) copy the explosion colours into move.w #$fd0,86(a0) the copper move.w #$f80,74(a0) move.w #$f80,90(a0) move.w #$c21,78(a0) move.w #$c21,94(a0) explode.ship addq.w #1,explosion.delay(a5) and.w #%11,explosion.delay(a5) bne return move.l explosion.ptr(a5),a0 points to an animation sequence clr.w d0 ended by 255 move.b (a0)+,d0 bmi game.over move.l a0,explosion.ptr(a5) move.l #ship.explosion,d1 mulu #312,d0 work out the next sprite address add.l d0,d1 lea sprite(pc),a0 moveq #2,d0 explode1 move.w d1,6(a0) and put it in the copper swap d1 move.w d1,2(a0) swap d1 add.w #104,d1 addq.l #8,a0 dbf d0,explode1 clr.w 2(a0) make sure outriders are not clr.w 6(a0) displayed rts game.over st.b kill.game(a5) rts collect.bonus move.w d0,d1 and.w #$6,d1 was it a foreground hit beq return if so no bonus tst.b bonus.mode(a5) beq return move.w bonus.num(a5),d1 beq bonus.score cmp.w #1,d1 beq max.canons cmp.w #2,d1 beq max.lasers cmp.w #3,d1 beq increase.speed cmp.w #4,d1 beq attach.mult cmp.w #5,d1 beq force.field addq.b #1,num.shields(a5) move.w #324-12,d0 final one is full shields move.w #128,ship.energy(a5) bsr max.energy bra collect.end bonus.score move.l #$1000,score.add(a5) bra collect.end max.canons addq.b #1,num.canons(a5) tst.b canons.on(a5) attach canons or power them up beq attach1 move.w #676-12,d0 move.w #128,canon.energy(a5) bsr max.energy bra collect.end attach1 st canons.on(a5) activate canons addq.b #1,ship.status(a5) bsr change.ship bra collect.end max.lasers addq.b #1,num.lasers(a5) tst.b lasers.on(a5) beq attach2 move.w #1028-12,d0 move.w #128,laser.energy(a5) bsr max.energy bra collect.end attach2 st lasers.on(a5) addq.b #2,ship.status(a5) bsr change.ship bra collect.end increase.speed cmp.w #8,ship.speed(a5) beq collect.end addq.b #1,num.speedups(a5) addq.w #1,ship.speed(a5) pixel speed between bra collect.end 1 & 7 only force.field addq.b #1,num.fields(a5) move.w #768,field.count(a5) set up the force field count move.w #$f,colours+74 make ship outline blue bra collect.end attach.mult tst.b mult1.on(a5) attach outriders bne attach.mult2 st mult1.on(a5) addq.b #1,num.outriders(a5) bra collect.end attach.mult2 addq.b #1,num.outriders(a5) st mult2.on(a5) collect.end clr.w d0 no collison move.l #path.buffer,a0 clr.w x.pos(a0) reset the bonus path clr.b bonus.mode(a5) move.w #$ffff,ship.count(a5) rts max.energy move.l #panel,a0 d0 = offset add.w d0,a0 moveq #7,d1 max.loop or.w #$5555,(a0) set all energy bits or.w #$5555,44(a0) or.w #$5555,88(a0) addq #2,a0 dbf d1,max.loop rts moveship tst.b ship.dead(a5) bne explode.ship tst.w field.count(a5) beq no.field move.w #$f,colours+74 subq.w #1,field.count(a5) decrement the force field bne no.field clr.w colours+74 outline back to black no.field btst #1,field.count+1(a5) check lsb beq no.field2 move.w #$00c,colours+74 no.field2 bsr joy read joystick & mouse tst.w ypos(a5) upper y limit of 0 bge up.ok clr.w d0 reset up flag if not allowed clr.w yvector(a5) and no y movement up.ok cmp.w #150,ypos(a5) maximum y value is 150 ble down.ok clr.w d1 if at max signal down no more clr.w yvector(a5) down.ok tst.w xpos(a5) minimum x position is 0 bge left.ok clr.w d3 clr.w xvector(a5) left.ok cmp.w #266,xpos(a5) maximum x position is 266 ble right.ok clr.w d2 clr.w xvector(a5) right.ok move.w ship.speed(a5),d4 d4 = ship speed move.w d4,d5 d5 = -ve ship speed neg.w d5 clr.w up.down(a5) make ship untilt move.w yvector(a5),d7 change the y vector first up tst.w d0 are we going up? beq down no, so check down move.w #-560,up.down(a5) yes, so tilt ship up (anims 560 bytes apart) cmp.w d7,d5 are we at max y speed beq right yes, so go and check x movement subq.w #1,d7 no, so decrease the vector bra right down tst.w d1 are we going down? beq right no, so check right move.w #560,up.down(a5) yes, so tilt the ship down cmp.w d7,d4 are we at max y speed beq right yes, so check x movement addq.w #1,d7 no, so increase the y vector right move.w d7,yvector(a5) store the new y vector move.w xvector(a5),d7 clr.w d6 now do the x vector which is tst.w d2 virtually identical to the y above beq left moveq #1,d6 cmp.w d7,d4 beq add.vectors addq #1,d7 bra add.vectors left tst.w d3 beq add.vectors moveq #-1,d6 cmp.w d7,d5 beq add.vectors subq #1,d7 add.vectors move.w d7,xvector(a5) or.w d2,d3 if we have moved left or right we bne checky may have to alter the animation move.w #4,mult.delay(a5) of the multiples moveq #1,d7 if the ship is not being moved but tst.w xvector(a5) still has some inertia then decrease beq checky the x & y vectors until they hit 0 bmi xto0 neg.w d7 xto0 add.w d7,xvector(a5) checky or.w d0,d1 bne add.vectors2 moveq #1,d7 tst.w yvector(a5) beq add.vectors2 bmi yto0 neg.w d7 yto0 add.w d7,yvector(a5) add.vectors2 move.w xpos(a5),d4 finally add the new vectors to move.w ypos(a5),d5 the x & y coordinates add.w xvector(a5),d4 add.w yvector(a5),d5 move.w d4,xpos(a5) move.w d5,ypos(a5) bsr xytosprite convert the xy coords into move.l shipaddress(a5),a0 hardware sprite format add.w up.down(a5),a0 add the up/down offset * now set up the four hardware sprite control words move.l d0,(a0) ship 1.1 (rear end) bset #7,d0 move.l d0,184(a0) ship 1.2 with attach bit set add.l #$0b080000,d0 add 11 to vstart & 16 to hstart bclr #7,d0 reset attach bit sub.w #$0b00,d0 vstop is 11 less move.l d0,2*184(a0) ship 1.3 (front) bset #7,d0 set attach move.l d0,2*184+96(a0) ship 1.4 bsr ship.to.copper put the address of the current subq.w #1,mult.delay(a5) ship in the copper bne same.outrider and finally work out which multiple move.w #4,mult.delay(a5) to display add.w d6,mult.number(a5) outriders must be between bne max.mult 1 & 5 move.w #1,mult.number(a5) max.mult cmp.w #6,mult.number(a5) bne same.outrider move.w #5,mult.number(a5) same.outrider bsr draw.outrider draw the multiple into the sprite bra check.firekey ************************************************************************** xytosprite * d4 = x coordinate * d5 = y coordinate * returns d0.l as the control words clr.l d0 return longword in do add.w #44-11,d5 hardware offset vertical lsl.w #8,d5 into bits 8-15 add.w #128,d4 horizontal offset lsr.w #1,d4 /2 low bit into extend or.w d5,d4 X intact move.w d4,d0 X still intact swap d0 ditto roxl.w #1,d0 get low bit of hstart into bit 0 add.w #$2c00,d5 calcualate vstop (+44 lines) or.w d5,d0 low word set up rts ************************************************************************** draw.outrider move.w mult.number(a5),d0 get the animation number tst.b mult1.on(a5) for the multiple bne mult1ok clr.w d0 mult1ok lea outriders,a0 base address of outriders mulu #44,d0 44 bytes per plane for pair add.w d0,a0 move.l a0,a1 a0 = plane 1 add.w #264,a1 a1 = plane 2 move.l shipaddress(a5),a2 current ship address add.w up.down(a5),a2 addq #4,a2 get past sprite header movem.l a0-a2,-(sp) moveq #10,d7 11 lines high out1 move.w (a0)+,(a2)+ move.w (a1)+,(a2)+ dbf d7,out1 tst.b mult2.on(a5) bne mult2ok lea outriders,a0 if mult 2 not on then move.l a0,a1 point the data to zeroes mult2ok add.w #22*2*2,a2 pass the ship graphics moveq #10,d7 and draw the bottom one out2 move.w (a0)+,(a2)+ move.w (a1)+,(a2)+ dbf d7,out2 planes 1 & 2 done movem.l (sp)+,a0-a2 get back pointers add.w #528,a0 a0 = plane 3 add.w #528,a1 a1 = plane 4 add.w #44*4+8,a2 next sprite moveq #10,d7 11 lines high out3 move.w (a0)+,(a2)+ move.w (a1)+,(a2)+ dbf d7,out3 tst.b mult2.on(a5) bne mult3ok lea outriders,a0 if mult 2 not on then move.l a0,a1 point the data to zeroes mult3ok add.w #22*2*2,a2 pass the ship graphics moveq #10,d7 and draw the bottom one out4 move.w (a0)+,(a2)+ move.w (a1)+,(a2)+ dbf d7,out4 planes 3 & 4 done rts ************************************************************************** check.firekey bsr get.firekey bne fire clr.b firekey(a5) rts fire tst.w fire.delay(a5) bne fire.end move.w #firedelay,fire.delay(a5) tst.b firekey(a5) beq test.missiles rts fire.end move.w #firedelay,fire.delay(a5) rts get.firekey move.b PortA,d0 not.b d0 and.b #$c0,d0 rts shift.coords lea xpos(a5),a2 move.w 16(a2),20(a2) move.w 18(a2),22(a2) move.w 12(a2),16(a2) move.w 14(a2),18(a2) move.w 8(a2),12(a2) move.w 10(a2),14(a2) move.w 4(a2),8(a2) move.w 6(a2),10(a2) move.w (a2),4(a2) move.w 2(a2),6(a2) rts test.missiles st firekey(a5) clr.w d0 0 for missile sound only tst.w canon.energy(a5) sne d1 and.w #1,d1 1 for canons only tst.w laser.energy(a5) sne d2 and.w #2,d2 2 for lasers only add.w d1,d0 add.w d2,d0 3 for all ; lea effects(pc),a0 ; move.b 0(a0,d0.w),d0 ; jsr initfx moveq #3,d7 fire3 btst d7,activemissiles(a5) beq initmissile dbf d7,fire3 test.canon tst.b canons.on(a5) beq test.lasers tst.w canon.energy(a5) beq test.lasers moveq #2,d7 fire1 btst d7,activecanons(a5) beq initcanon dbf d7,fire1 test.lasers tst.b lasers.on(a5) beq test.mult1 tst.w laser.energy(a5) beq test.mult1 moveq #2,d7 fire4 btst d7,activelasers(a5) beq initlaser dbf d7,fire4 test.mult1 tst.b mult1.on(a5) beq test.mult2 moveq #1,d7 fire5 btst d7,activemult1(a5) beq init.mult1 dbf d7,fire5 test.mult2 tst.b mult2.on(a5) beq fire7 moveq #1,d7 fire6 btst d7,activemult2(a5) beq init.mult2 dbf d7,fire6 fire7 rts init.mult1 bset d7,activemult1(a5) lea mult1data(a5),a0 lsl.w #3,d7 add.w d7,a0 move.w xpos(a5),d0 add.w #38,d0 move.w d0,(a0)+ move.w ypos(a5),d0 addq #6,d0 move.w d0,(a0)+ move.w mult.number(a5),d0 subq.w #1,d0 lsl.w #1,d0 lea mult1offsets(pc),a1 move.b 0(a1,d0.w),(a0)+ move.b 1(a1,d0.w),(a0)+ move.w #16,(a0)+ bra test.mult2 init.mult2 bset d7,activemult2(a5) lea mult2data(a5),a0 lsl.w #3,d7 add.w d7,a0 move.w xpos(a5),d0 add.w #38,d0 move.w d0,(a0)+ move.w ypos(a5),d0 add.w #40,d0 move.w d0,(a0)+ move.w mult.number(a5),d0 subq.w #1,d0 lsl.w #1,d0 lea mult2offsets(pc),a1 move.b 0(a1,d0.w),(a0)+ move.b 1(a1,d0.w),(a0)+ move.w #16,(a0)+ rts initmissile bset d7,activemissiles(a5) lea missiledata(a5),a0 lsl.w #3,d7 add.w d7,a0 move.w xpos(a5),d0 add.w #58,d0 move.w d0,(a0)+ move.w ypos(a5),d0 add.w #24,d0 move.w d0,(a0)+ move.w #16,(a0)+ bra test.canon initcanon bset d7,activecanons(a5) lea canondata(a5),a0 lsl.w #3,d7 add.w d7,a0 move.w xpos(a5),d0 add.w #53,d0 move.w d0,(a0)+ move.w ypos(a5),d0 add.w #30,d0 move.w d0,(a0)+ move.w #12,(a0)+ move.w #676,d0 subq.w #2,canon.energy(a5) move.w canon.energy(a5),d1 bsr decrease.energy bra test.lasers initlaser bset d7,activelasers(a5) lea laserdata(a5),a0 lsl.w #3,d7 add.w d7,a0 move.w xpos(a5),d0 add.w #42,d0 move.w d0,(a0)+ move.w ypos(a5),d0 add.w #14,d0 move.w d0,(a0)+ move.w #32,(a0)+ move.w #1028,d0 subq.w #2,laser.energy(a5) move.w laser.energy(a5),d1 bsr decrease.energy bra test.mult1 decrease.energy move.l #panel,a1 d0 = offset add.w d0,a1 d1 = energy value (0-128) ; 324 for ship energy ; 676 for canons lsr.w #4,d1 1028 for lasers lsl.w #1,d1 a1 = plane1 add.w d1,a1 move.w (a1),d1 move.w d1,d2 and.w #$5555,d1 get energy bits only and.w #$aaaa,d2 preserve panel bits lsl.w #2,d1 shift into next space or.w d1,d2 move.w d2,(a1) add.w #44,a1 move.w (a1),d2 and.w #$aaaa,d2 or.w d1,d2 new energy into panel move.w d2,(a1) add.w #44,a1 move.w (a1),d2 and.w #$aaaa,d2 or.w d1,d2 move.w d2,(a1) rts ************************************************************************** setup.mouse move.w joy0dat(a6),d4 read the mouse x,y position so move.w d4,-(sp) and.w #$ff,d4 the ship doesnt jump when we move.w d4,oldmousex(a5) start move.w (sp)+,d4 lsr.w #8,d4 move.w d4,oldmousey(a5) rts joy move.w #$0100,d0 setup the mask for each bit in move.w #$0001,d1 the joystick register move.w #$0002,d2 the routine returns left/right move.w #$0200,d3 /up/down in d0..d3 move.w joy1dat(a6),d4 if the corresponding data register and.w d4,d0 is not = 0 then the joystick and.w d4,d1 had been pressed in that direction and.w d4,d2 and.w d4,d3 lsl.w #1,d0 lsl.w #1,d1 eor.w d2,d1 eor.w d3,d0 move.w joy0dat(a6),d4 read the mouse counters, if a move move.w d4,-(sp) has been detected then set the and.w #$ff,d4 appropiate joystick registers sub.w oldmousex(a5),d4 to mimick a joystick move beq noxmove bmi leftmove this is not a proper proportional moveq #1,d2 read but a simple up/dowm/left/right bra noxmove check leftmove moveq #1,d3 noxmove move.w (sp),d4 lsr.w #8,d4 sub.w oldmousey(a5),d4 beq joyend bmi upmove moveq #1,d1 bra joyend upmove moveq #1,d0 joyend move.w (sp),d4 and.w #$ff,d4 move.w d4,oldmousex(a5) save the mouse values for comparison move.w (sp)+,d4 next time around lsr.w #8,d4 move.w d4,oldmousey(a5) rts ************************************************************************** ship.to.copper move.l shipaddress(a5),a1 get the current ship address add.w up.down(a5),a1 and update the four sprite move.l a1,d0 pointers in the copperlist move.l a1,d1 move.l a1,d2 move.l a1,d3 add.w #184,d1 work out the address of each add.w #184*2,d2 hardware sprite add.w #184*2+96,d3 lea sprite(pc),a0 move.w d0,6(a0) swap d0 move.w d0,2(a0) move.w d1,14(a0) swap d1 move.w d1,10(a0) move.w d2,22(a0) swap d2 move.w d2,18(a0) move.w d3,30(a0) swap d3 move.w d3,26(a0) rts ************************************************************************** change.ship clr.w d0 move.b ship.status(a5),d0 1 = canons, 2 = lasers, 3 = both lea ship1.2(pc),a0 mulu #1680,d0 968 bytes for the four sprites add.l d0,a0 per ship move.l a0,shipaddress(a5) store the ship address rts ************************************************************************** restorebgnds bsr getscreeninfo clr.w bltamod(a6) move.l d0,bltapt(a6) set blitter A channel to the saved clr.w bltcon1(a6) background data restoreloop move.w (a0)+,d1 fetch the blit size beq return once zero all have been replaced move.w d1,d3 addq #2,a0 and.w #$3f,d1 work out the length in bytes lsl.w #1,d1 move.w #100,d2 subtract from the screen width sub.w d1,d2 to give the destination modulo move.w d2,bltdmod(a6) move.w #$09f0,bltcon0(a6) use D = A for the blit move.l (a0)+,bltdpt(a6) and do all three planes. move.w d3,bltsize(a6) move.l (a0)+,bltdpt(a6) move.w d3,bltsize(a6) move.l (a0)+,bltdpt(a6) move.w d3,bltsize(a6) bra restoreloop savebgnds bsr check.end.screen watch out for screen wraparound bsr coords.to.pf1offsets convert pixel coords to byte offsets move.w #aliensize,d3 move.w #94,bltamod(a6) clr.w bltdmod(a6) clr.w bltcon1(a6) move.w #$09f0,bltcon0(a6) use D = A for the blit bsr setup.addresses save the blitsize and addresses bsr blit.to.buffer and save the background data rts ************************************************************************** drawbobs move.w #94,bltdmod(a6) set up the destination modulos move.w #94,bltcmod(a6) clr.l d6 d6 will hold an offset if the tst.b upsidedown(a5) bob is drawn upside down beq normal move.w #-106,bltdmod(a6) draw from the bottom up by using move.w #-106,bltcmod(a6) a negative modulo move.l #23*100,d6 normal move.w (a0),d3 get the blitsize in d3 move.w 2(a0),d1 the scroll value in d1 (0-15) ror.w #4,d1 move.w d1,bltcon1(a6) set up the B scroll value or.w #$0fca,d1 set up the A scroll value and the move.w d1,bltcon0(a6) minterm for D = notA.C + B move.w #-2,bltbmod(a6) move.w #-2,bltamod(a6) move.l a1,bltbpt(a6) bsr blit.to.backgnd draw to the screen rts ************************************************************************** getscreeninfo * returns the address in a0 of the data listing the screeen locations * where the backgrounds have to be replaced * d0 points to the buffer containing the saved backgrounds tst.b screen.num(a5) double buffering means we have bne getscreen1 to have two lists running move.l #buffer0,d0 move.l #screen0bgnds,a0 rts getscreen1 move.l #buffer1,d0 move.l #screen1bgnds,a0 rts ************************************************************************** process.aliens clr.w all.coords(a5) move.l #path.buffer,a0 lea alien.buffer(a5),a1 where to store the info moveq #11,d7 12 aliens max process.loop move.w table.offset(a0),d0 get offset in d0 move.b mode(a0),d6 d6 contains the mode byte move.w x.pos(a0),d1 beq finished alien dead clr.w last.x(a5) clr.w last.y(a5) move.w y.pos(a0),d2 subq.b #1,anim.delay(a0) bne same.anim move.b num.anims(a0),d3 beq same.anim btst #3,d6 beq up.only btst #4,d6 bne down.anim addq.b #1,anim.num(a0) increase anim num cmp.b anim.num(a0),d3 bne process1 bchg #4,d6 bra process1 down.anim subq.b #1,anim.num(a0) bpl process1 move.b #1,anim.num(a0) bchg #4,d6 bra process1 up.only addq.b #1,anim.num(a0) next animation addq.b #1,d3 cmp.b anim.num(a0),d3 wrap around anims bne process1 clr.b anim.num(a0) tst.b sprite.num(a0) was it an explosion bne process1 clr.w x.pos(a0) yes so move.w d1,last.x(a5) store its coords move.w d2,last.y(a5) clr.w d1 kill this alien bra finished process1 move.b anim.delay2(a0),anim.delay(a0) restore the delay same.anim tst.b sprite.num(a0) beq finished dont move explosions tst.b pause.count(a0) beq no.pause no pause cmp.b #$ff,pause.count(a0) beq finished ff means pause forever... subq.b #1,pause.count(a0) beq update if zero update the offset bra finished not zero so do nufink no.pause clr.w d3 clr.w d4 clr.w d5 move.b speed(a0),d5 speed in d5 move.b 0(a0,d0.w),d3 d3 is the x coord to go to move.b 1(a0,d0.w),d4 d4 is the y coord to go to bsr check.seek check all seek bits tst.b sprite.num(a0) beq store.coords a heat seeker may have exploded btst #0,d6 test for offset mode bne add.offsets tst.w d3 if x goto is minus then bmi check.y leave x coord alone lsl.w #1,d3 even coord only cmp.w d3,d1 check difference between the sne x.equal(a5) two x coords beq check.y blt increase.x if d1