10 REM ------------------------------------------
   20 REM Pixel Fandango Space Fighter X
   30 REM ------------------------------------------
   40 DIM images% 280
   50 workImage%=images%
   60 MODE 1
   70 REM Set colour palette...
   80 VDU 19,1,2,0,0,0
   90 VDU 19,2,6,0,0,0
  100 VDU 19,3,3,0,0,0
  110 COL_EXPLODE=3
  120 REM Create alien flight path data...
  130 DIM pathData% 550
  140 FLIGHT_PATH_SIZE=255
  150 FLIGHT_PATH_IX=220
  160 FLIGHT_PATH_IY=950
  170 endOfPathData%=FN_InitFlightPattern(pathData%)
  180 REM Add graphic image definitions...
  190 rocketImage%=workImage%
  200 workImage%=FN_AddRocketImage(rocketImage%)
  210 alien1Image%=workImage%
  220 workImage%=FN_AddAlien1Image(alien1Image%)
  230 bulletImage%=workImage%
  240 workImage%=FN_AddBulletImage(bulletImage%)
  250 explosionImage%=workImage%
  260 workImage%=FN_AddExplosionImage(explosionImage%)
  270 bigExplosionImage%=workImage%
  280 workImage%=FN_AddBigExplosionImage(bigExplosionImage%)
  290 REM Entity States...
  300 DEAD_ENTITY=0
  310 ALIEN_LIVE=20
  320 ALIEN_EXPLODE=ALIEN_LIVE-1
  330 PLAYER_LIVE=200
  340 PLAYER_EXPLODE=PLAYER_LIVE-1
  350 REM Base entity field offsets...
  360 eENTITY_SIZE=26
  370 eTYPE=0
  380 eSIZE=1
  390 eIMAGE=2
  400 eSTATE=6
  410 eCOLOUR=7
  420 eXPOS=8
  430 eYPOS=12
  440 eHWIDTH=16
  450 eHHEIGHT=17
  460 eXCENTRE=18
  470 eYCENTRE=22
  480 REM Special fields above base entity
  490 eFLIGHT_PATH_INDEX=eENTITY_SIZE+0
  500 REM Entity types
  510 ePLAYER=0
  520 eBULLET=1
  530 eBOMB=2
  540 eALIEN=3
  550 REM Other global settings...
  560 BOMB_SPEED=12
  570 BULLET_SPEED=20
  580 PLAYER_START_X=600
  590 PLAYER_START_Y=40
  600 REM Add entities...
  610 pNext%=0
  620 DIM entities% 2500
  630 REPEAT
  640   REM Player's rocket...
  650   pRocket%=entities%
  660   rX%=PLAYER_START_X:rY%=PLAYER_START_Y
  670   pNext%=FN_InitEntity(ePLAYER, 0, pRocket%, rocketImage%, PLAYER_LIVE, 2, rX%, rY%)
  680   REM Aliens...
  690   MaxAliens%=20
  700   pAliens%=pNext%
  710   FOR A=0 TO MaxAliens%
  720     pNext%=FN_InitAlien(eALIEN, pNext%, alien1Image%, DEAD_ENTITY, 3, FLIGHT_PATH_IX, FLIGHT_PATH_IY, FLIGHT_PATH_SIZE)
  730   NEXT A
  740   REM Bullets...
  750   MaxBullets%=10
  760   pBullets%=pNext%
  770   FOR B=0 TO MaxBullets%
  780     pNext%=FN_InitEntity(eBULLET, 0, pNext%, bulletImage%, 0, 2, 0, 0)
  790   NEXT B
  800   pNextBullet%=pBullets%
  810   pEndBullets%=pNext%
  820   REM Bombs...
  830   MaxBombs%=50
  840   pBombs%=pNext%
  850   FOR B=0 TO MaxBombs%
  860     pNext%=FN_InitEntity(eBOMB, 0, pNext%, bulletImage%, 0, 3, 0, 0)
  870   NEXT B
  880   pNextBomb%=pBombs%
  890   pEndBombs%=pNext%
  900   canFire%=0
  910   CLS:VDU 5
  920   MOVE 0, 128
  930   GCOL 0,1
  940   PRINT "Used Image Space:" workImage%-images%
  950   PRINT "Used Entity Space:" pNext%-entities%
  960   PRINT "Used F-Path Data:" endOfPathData%-pathData%
  970   MOVE 410,650:PRINT"PIXEL FANDANGO"
  980   MOVE 395,600:PRINT"SPACE-FIGHTER-X"
  990   REM Clear keyboard buffer...
 1000   *FX 15
 1010   MOVE 430,550:PRINT"PRESS ANY KEY"
 1020   a%=GET
 1030   CLS:VDU 5
 1040   score%=0
 1050   lastScore%=0
 1060   lives%=3
 1070   spawnSize%=4
 1080   REM Game loop...
 1090   REPEAT
 1100     PROC_NewPlayer(pRocket%, rocketImage%)
 1110     PROC_MoveEntityTo(pRocket%, rX%, rY%)
 1120     cycle%=0
 1130     alienSpawn%=0
 1140     REPEAT
 1150       cycle%=cycle%+1
 1160       IF score%<>lastScore% THEN MOVE 300,1000:GCOL 0,0:PRINT "SCORE:";lastScore%:lastScore%=score%
 1170       MOVE 300,1000:GCOL 0,3:PRINT "SCORE:";score%
 1180       MOVE 800,1000:GCOL 0,3:PRINT "LIVES:";lives%
 1190       pPlayerState%=pRocket%+eSTATE
 1200       REM draw aliens...
 1210       workAlien%=pAliens%
 1220       nLiveAliens%=0
 1230       FOR A=0 TO MaxAliens%
 1240         REM Update explosion count (if in exploding state)
 1250         pAlienState%=workAlien%+eSTATE
 1260         IF ?(pAlienState%)=1 PROC_DrawEntity(workAlien%, 0):?(workAlien%+eSTATE)=0
 1270         IF ?(pAlienState%)>0 AND ?(pAlienState%)<20 THEN ?(pAlienState%)=?(pAlienState%)-1:PROC_DrawEntity(workAlien%, COL_EXPLODE)
 1280         isAlive%=?(pAlienState%)>=20
 1290         IF isAlive% AND ?(pPlayerState%)=PLAYER_LIVE AND RND(1000)<15 THEN pNextBomb%=FN_DropBomb(workAlien%, pNextBomb%):IF pNextBomb%>=pEndBombs% THEN pNextBomb%=pBombs%
 1300         IF isAlive% THEN workAlien%=FN_UpdateAlien(workAlien%, pBullets%, pathData%, explosionImage%) ELSE workAlien%=FN_NextEntity(workAlien%)
 1310         IF isAlive% THEN nLiveAliens%=nLiveAliens%+1
 1320       NEXT A
 1330       IF nLiveAliens%=0 AND alienSpawn%=0 THEN alienSpawn%=spawnSize%:IF spawnSize%<MaxAliens% THEN spawnSize%=spawnSize%+1
 1340       IF cycle% MOD 5 = 0 AND alienSpawn%>0 THEN PROC_StartAlien(pAliens%):alienSpawn%=alienSpawn%-1
 1350       REM draw bullets...
 1360       workBullet%=pBullets%
 1370       FOR B=0 TO MaxBullets%
 1380         workBullet%=FN_UpdateBullet(workBullet%, BULLET_SPEED)
 1390       NEXT B
 1400       workBomb%=pBombs%
 1410       FOR B=0 TO MaxBombs%
 1420         workBomb%=FN_UpdateBullet(workBomb%, BOMB_SPEED)
 1430       NEXT B
 1440       REM handle user input...
 1450       newX%=rX%
 1460       IF INKEY(-98) THEN newX%=newX%-12:IF newX%<32 THEN newX%=32
 1470       IF INKEY(-67) THEN newX%=newX%+12:IF newX%>1150 THEN newX%=1150
 1480       IF INKEY(-74)=0 AND ?(pPlayerState%)=PLAYER_LIVE THEN canFire%=1
 1490       IF canFire%=1 AND INKEY(-74) THEN pNextBullet%=FN_SetBullet(pNextBullet%,1,rX%+50,rY%+90):canFire%=0
 1500       IF pNextBullet%>=pEndBullets% THEN pNextBullet%=pBullets%
 1510       REM Wait for screen refresh sync...
 1520       *FX19
 1530       IF newX%<>rX% AND ?(pPlayerState%)=PLAYER_LIVE THEN PROC_MoveEntityTo(pRocket%, newX%, rY%):rX%=newX%
 1540       IF ?(pPlayerState%)<PLAYER_LIVE THEN ?(pPlayerState%)=?(pPlayerState%)-1
 1550       IF FN_IsPlayerCollision(pRocket%, pBombs%) THEN PROC_KillPlayer(pRocket%, bigExplosionImage%):canFire%=0
 1560     UNTIL ?(pRocket%+eSTATE)=0
 1570     MOVE 800,1000:GCOL 0,0:PRINT "LIVES:";lives%
 1580     lives%=lives%-1
 1590   UNTIL lives%=0
 1600   CLS
 1610   GCOL 0,1
 1620   VDU 5:MOVE 500,550:PRINT"GAME OVER"
 1630 UNTIL 0
 1640 END
 1650 REM --------------------------------------------------
 1660 REM Functions to handle graphic image definitions
 1670 REM --------------------------------------------------
 1680 REM
 1690 REM --------------------------
 1700 REM Function to add image defn
 1710 REM header information for
 1720 REM collision detection
 1730 REM --------------------------
 1740 DEF FN_AddImageHeader(address%, centreX%, centreY%, collnRadius%)
 1750 ?(address%+0)=centreX%
 1760 ?(address%+1)=centreY%
 1770 ?(address%+2)=collnRadius%
 1780 =address%+3
 1790 REM --------------------------
 1800 REM Function to add an image
 1810 REM part to defn at address
 1820 REM type: 0=end 1=MOVE, 2=DRAW
 1830 REM x,y are coords from TL
 1840 REM Returns next free address
 1850 REM --------------------------
 1860 DEF FN_AddImagePart(address%, type%, x%, y%)
 1870 ?(address%+0)=type%
 1880 ?(address%+1)=x%
 1890 ?(address%+2)=y%
 1900 =address%+3
 1910 REM
 1920 DEF FN_AddImagePartScaled(address%, type%, x%, y%, scale)
 1930 ?(address%+0)=type%
 1940 ?(address%+1)=INT(x%*scale)
 1950 ?(address%+2)=INT(y%*scale)
 1960 =address%+3
 1970 REM
 1980 REM --------------------------
 1990 REM Functions to add images
 2000 REM --------------------------
 2010 DEF FN_AddRocketImage(address%)
 2020 rScale=0.8
 2030 address%=FN_AddImageHeader(address%, INT(70*rScale), INT(60*rScale), INT(64*rScale))
 2040 address%=FN_AddImagePartScaled(address%, 1, 80, 40, rScale)
 2050 address%=FN_AddImagePartScaled(address%, 2, 100, 20, rScale)
 2060 address%=FN_AddImagePartScaled(address%, 2, 80, 0, rScale)
 2070 address%=FN_AddImagePartScaled(address%, 2, 60, 0, rScale)
 2080 address%=FN_AddImagePartScaled(address%, 2, 40, 20, rScale)
 2090 address%=FN_AddImagePartScaled(address%, 2, 60, 40, rScale)
 2100 address%=FN_AddImagePartScaled(address%, 2, 80, 40, rScale)
 2110 address%=FN_AddImagePartScaled(address%, 2, 80, 80, rScale)
 2120 address%=FN_AddImagePartScaled(address%, 2, 100, 60, rScale)
 2130 address%=FN_AddImagePartScaled(address%, 2, 70, 120, rScale)
 2140 address%=FN_AddImagePartScaled(address%, 2, 80, 80, rScale)
 2150 address%=FN_AddImagePartScaled(address%, 2, 60, 80, rScale)
 2160 address%=FN_AddImagePartScaled(address%, 2, 70, 120, rScale)
 2170 address%=FN_AddImagePartScaled(address%, 2, 40, 60, rScale)
 2180 address%=FN_AddImagePartScaled(address%, 2, 60, 80, rScale)
 2190 address%=FN_AddImagePartScaled(address%, 2, 60, 40, rScale)
 2200 REM left wing
 2210 address%=FN_AddImagePartScaled(address%, 1, 20, 60, rScale)
 2220 address%=FN_AddImagePartScaled(address%, 2, 0, 80, rScale)
 2230 address%=FN_AddImagePartScaled(address%, 2, 0, 40, rScale)
 2240 address%=FN_AddImagePartScaled(address%, 2, 20, 20, rScale)
 2250 address%=FN_AddImagePartScaled(address%, 2, 20, 60, rScale)
 2260 address%=FN_AddImagePartScaled(address%, 2, 40, 60, rScale)
 2270 address%=FN_AddImagePartScaled(address%, 2, 40, 20, rScale)
 2280 address%=FN_AddImagePartScaled(address%, 2, 20, 20, rScale)
 2290 REM right wing
 2300 address%=FN_AddImagePartScaled(address%, 1, 120, 60, rScale)
 2310 address%=FN_AddImagePartScaled(address%, 2, 140, 80, rScale)
 2320 address%=FN_AddImagePartScaled(address%, 2, 140, 40, rScale)
 2330 address%=FN_AddImagePartScaled(address%, 2, 120, 20, rScale)
 2340 address%=FN_AddImagePartScaled(address%, 2, 120, 60, rScale)
 2350 address%=FN_AddImagePartScaled(address%, 2, 100, 60, rScale)
 2360 address%=FN_AddImagePartScaled(address%, 2, 100, 20, rScale)
 2370 address%=FN_AddImagePartScaled(address%, 2, 120, 20, rScale)
 2380 ?(address%)=0
 2390 =address%+1
 2400 DEF FN_AddAlien1Image(address%)
 2410 aScale=1.4
 2420 address%=FN_AddImageHeader(address%, INT(25*aScale), INT(20*aScale), INT(20*aScale))
 2430 address%=FN_AddImagePartScaled(address%, 1, 40, 30, aScale)
 2440 address%=FN_AddImagePartScaled(address%, 2, 40, 10, aScale)
 2450 address%=FN_AddImagePartScaled(address%, 2, 50, 0, aScale)
 2460 address%=FN_AddImagePartScaled(address%, 2, 50, 20, aScale)
 2470 address%=FN_AddImagePartScaled(address%, 2, 30, 40, aScale)
 2480 address%=FN_AddImagePartScaled(address%, 2, 20, 40, aScale)
 2490 address%=FN_AddImagePartScaled(address%, 2, 0, 20, aScale)
 2500 address%=FN_AddImagePartScaled(address%, 2, 0, 0, aScale)
 2510 address%=FN_AddImagePartScaled(address%, 2, 10, 10, aScale)
 2520 address%=FN_AddImagePartScaled(address%, 2, 10, 30, aScale)
 2530 address%=FN_AddImagePartScaled(address%, 2, 10, 10, aScale)
 2540 address%=FN_AddImagePartScaled(address%, 2, 20, 0, aScale)
 2550 address%=FN_AddImagePartScaled(address%, 2, 30, 0, aScale)
 2560 address%=FN_AddImagePartScaled(address%, 2, 40, 10, aScale)
 2570 address%=FN_AddImagePartScaled(address%, 1, 15, 20, aScale)
 2580 address%=FN_AddImagePartScaled(address%, 2, 35, 20, aScale)
 2590 address%=FN_AddImagePartScaled(address%, 2, 35, 30, aScale)
 2600 address%=FN_AddImagePartScaled(address%, 2, 25, 20, aScale)
 2610 address%=FN_AddImagePartScaled(address%, 2, 15, 30, aScale)
 2620 address%=FN_AddImagePartScaled(address%, 2, 15, 20, aScale)
 2630 ?(address%)=0
 2640 =address%+1
 2650 DEF FN_AddBulletImage(address%)
 2660 address%=FN_AddImageHeader(address%, 3, 8, 5)
 2670 address%=FN_AddImagePart(address%, 1, 0, 0)
 2680 address%=FN_AddImagePart(address%, 2, 6, 0)
 2690 address%=FN_AddImagePart(address%, 2, 6, 16)
 2700 address%=FN_AddImagePart(address%, 2, 0, 16)
 2710 address%=FN_AddImagePart(address%, 2, 0, 0)
 2720 ?(address%)=0
 2730 =address%+1
 2740 DEF FN_AddExplosionImage(address%)
 2750 address%=FN_AddImageHeader(address%, 25, 25, 25)
 2760 address%=FN_AddImagePart(address%, 1, 0, 0)
 2770 address%=FN_AddImagePart(address%, 2, 10, 20)
 2780 address%=FN_AddImagePart(address%, 2, 0, 30)
 2790 address%=FN_AddImagePart(address%, 2, 15, 30)
 2800 address%=FN_AddImagePart(address%, 2, 20, 50)
 2810 address%=FN_AddImagePart(address%, 2, 30, 30)
 2820 address%=FN_AddImagePart(address%, 2, 50, 40)
 2830 address%=FN_AddImagePart(address%, 2, 40, 20)
 2840 address%=FN_AddImagePart(address%, 2, 50, 10)
 2850 address%=FN_AddImagePart(address%, 2, 35, 10)
 2860 address%=FN_AddImagePart(address%, 2, 30, 0)
 2870 address%=FN_AddImagePart(address%, 2, 20, 10)
 2880 address%=FN_AddImagePart(address%, 2, 0, 0)
 2890 ?(address%)=0
 2900 =address%+1
 2910 DEF FN_AddBigExplosionImage(address%)
 2920 address%=FN_AddImageHeader(address%, 50, 50, 50)
 2930 address%=FN_AddImagePart(address%, 1, 0, 0)
 2940 address%=FN_AddImagePart(address%, 2, 20, 40)
 2950 address%=FN_AddImagePart(address%, 2, 0, 60)
 2960 address%=FN_AddImagePart(address%, 2, 30, 60)
 2970 address%=FN_AddImagePart(address%, 2, 40, 100)
 2980 address%=FN_AddImagePart(address%, 2, 60, 60)
 2990 address%=FN_AddImagePart(address%, 2, 100, 80)
 3000 address%=FN_AddImagePart(address%, 2, 80, 40)
 3010 address%=FN_AddImagePart(address%, 2, 100, 20)
 3020 address%=FN_AddImagePart(address%, 2, 70, 20)
 3030 address%=FN_AddImagePart(address%, 2, 60, 0)
 3040 address%=FN_AddImagePart(address%, 2, 40, 20)
 3050 address%=FN_AddImagePart(address%, 2, 0, 0)
 3060 ?(address%)=0
 3070 =address%+1
 3080 REM
 3090 REM --------------------------
 3100 REM Proc to draw image from
 3110 REM data at address in pos x,y
 3120 REM --------------------------
 3130 DEF PROC_DrawImage(pImage%, x%, y%)
 3140 REM Skip the header information...
 3150 pImage%=pImage%+3
 3160 REM Draw each image part...
 3170 REPEAT
 3180   pImage%=FN_DrawImagePart(pImage%, x%, y%)
 3190 UNTIL pImage%=0
 3200 ENDPROC
 3210 REM
 3220 REM --------------------------
 3230 REM Function to draw single
 3240 REM part of an image defn
 3250 REM and return next address
 3260 REM or 0 if its the last part
 3270 REM --------------------------
 3280 DEF FN_DrawImagePart(pPart%, x%, y%)
 3290 REM Return 0 if this item is an end marker
 3300 IF ?pPart%=0 THEN =0
 3310 REM Either move or draw to a point
 3320 IF ?(pPart%)=1 THEN MOVE ?(pPart%+1)+x%, ?(pPart%+2)+y%
 3330 IF ?(pPart%)=2 THEN DRAW ?(pPart%+1)+x%, ?(pPart%+2)+y%
 3340 REM return next address
 3350 =pPart%+3
 3360 REM
 3370 REM --------------------------------------------------
 3380 REM Functions to handle game entities
 3390 REM --------------------------------------------------
 3400 REM
 3410 REM --------------------------
 3420 REM Initialise a new entity
 3430 REM Return next address
 3440 REM --------------------------
 3450 DEF FN_InitEntity(typeId%, addSize%, pEntity%, pImage%, state%, colour%, x%, y%)
 3460 REM Record basic entity parameters
 3470 ?pEntity%=typeId%
 3480 ?(pEntity%+eSIZE)=eENTITY_SIZE+addSize%
 3490 !(pEntity%+eIMAGE)=pImage%
 3500 ?(pEntity%+eSTATE)=state%
 3510 ?(pEntity%+eCOLOUR)=colour%
 3520 !(pEntity%+eXPOS)=x%
 3530 !(pEntity%+eYPOS)=y%
 3540 REM Calc offsets for collision detection...
 3550 ?(pEntity%+eHWIDTH)=?(!(pEntity%+eIMAGE)+0)
 3560 ?(pEntity%+eHHEIGHT)=?(!(pEntity%+eIMAGE)+1)
 3570 REM Reserve space for centreX and centreY
 3580 REM calcs on move for collision detection
 3590 !(pEntity%+eXCENTRE)=0
 3600 !(pEntity%+eYCENTRE)=0
 3610 REM Anything after this is specific to entity type
 3620 =pEntity%+?(pEntity%+eSIZE)
 3630 REM --------------------------
 3640 REM Draw an entity
 3650 REM Return next address
 3660 REM --------------------------
 3670 DEF PROC_DrawEntity(pEntity%, colour%)
 3680 GCOL 0,colour%
 3690 PROC_DrawImage(!(pEntity%+eIMAGE), !(pEntity%+eXPOS), !(pEntity%+eYPOS))
 3700 ENDPROC
 3710 REM
 3720 REM --------------------------
 3730 REM Calc collision range
 3740 REM based on position, width,
 3750 REM height and radius.
 3760 REM --------------------------
 3770 DEF PROC_SetCollnCentre(pEntity%)
 3780 !(pEntity%+eXCENTRE)=!(pEntity%+eXPOS)+?(pEntity%+eHWIDTH)
 3790 !(pEntity%+eYCENTRE)=!(pEntity%+eYPOS)+?(pEntity%+eHHEIGHT)
 3800 ENDPROC
 3810 REM
 3820 REM --------------------------
 3830 REM Move an entity (relative)
 3840 REM --------------------------
 3850 DEF FN_MoveEntity(pEntity%, dx, dy)
 3860 REM Only move if state > 0 (is active)
 3870 IF ?(pEntity%+eSTATE)=0 THEN =pEntity%+?(pEntity%+eSIZE)
 3880 PROC_DrawEntity(pEntity%, 0)
 3890 pX%=!(pEntity%+eXPOS)+dx
 3900 pY%=!(pEntity%+eYPOS)+dy
 3910 IF pX%>1280 THEN pX%=pX%-1280
 3920 IF pX%<0 THEN pX%=pX%+1280
 3930 IF pY%>1024 THEN pY%=pY%-1024
 3940 IF pY%<0 THEN pY%=pY%+1024
 3950 !(pEntity%+eXPOS)=pX%
 3960 !(pEntity%+eYPOS)=pY%
 3970 PROC_SetCollnCentre(pEntity%)
 3980 PROC_DrawEntity(pEntity%, ?(pEntity%+eCOLOUR))
 3990 =pEntity%+?(pEntity%+eSIZE)
 4000 REM
 4010 REM --------------------------
 4020 REM Move an entity (absolute)
 4030 REM --------------------------
 4040 DEF PROC_MoveEntityTo(pEntity%, x%, y%)
 4050 REM Only move if state > 0 (is active)
 4060 IF ?(pEntity%+eSTATE)=0 THEN =pEntity+?(pEntity%+eSIZE)
 4070 PROC_DrawEntity(pEntity%, 0)
 4080 !(pEntity%+eXPOS)=x%
 4090 !(pEntity%+eYPOS)=y%
 4100 PROC_SetCollnCentre(pEntity%)
 4110 PROC_DrawEntity(pEntity%, ?(pEntity%+eCOLOUR))
 4120 ENDPROC
 4130 REM
 4140 REM --------------------------
 4150 REM Get pointer to next entity
 4160 REM --------------------------
 4170 DEF FN_NextEntity(pEntity%)
 4180 =pEntity%+?(pEntity%+eSIZE)
 4190 REM
 4200 REM --------------------------
 4210 REM Collision Detection
 4220 REM lhs, rhs, top, bot collision
 4230 REM range pre calc'd on entity move
 4240 REM --------------------------
 4250 DEF FN_IsCollision(pEntity1%, pEntity2%, radius%)
 4260 REM Only check if both entities are active
 4270 IF ?(pEntity1%+eSTATE)=0 OR ?(pEntity2%+eSTATE)=0 = 0
 4280 dX=ABS(!(pEntity1%+eXCENTRE)-!(pEntity2%+eXCENTRE))
 4290 dY=ABS(!(pEntity1%+eYCENTRE)-!(pEntity2%+eYCENTRE))
 4300 IF dX<radius% AND dY<radius% =1
 4310 =0
 4320 REM --------------------------------------------------
 4330 REM Specific entity functions
 4340 REM --------------------------------------------------
 4350 DEF FN_UpdateBullet(pBullet%, speed%)
 4360 REM Is bullet active?
 4370 pState%=pBullet%+eSTATE
 4380 IF ?(pState%)=0 THEN =pBullet%+?(pBullet%+eSIZE)
 4390 IF ?(pState%)=1 THEN pNext% = FN_MoveEntity(pBullet%, 0, speed%)
 4400 IF ?(pState%)=2 THEN pNext% = FN_MoveEntity(pBullet%, 0, -speed%)
 4410 IF ?(pState%)=3 THEN ?(pState%)=0 : PROC_DrawEntity(pBullet%, 0)
 4420 IF !(pBullet%+eYPOS)>1000 OR !(pBullet%+eYPOS)<24 THEN ?(pState%)=3
 4430 =pBullet%+?(pBullet%+eSIZE)
 4440 REM --------------------------------------------------
 4450 DEF FN_SetBullet(pBullet%, state%, x%, y%)
 4460 ?(pBullet%+eSTATE)=state%
 4470 !(pBullet%+eXPOS)=x%
 4480 !(pBullet%+eYPOS)=y%
 4490 PROC_SetCollnCentre(pBullet%)
 4500 IF state%=1 THEN SOUND 1,-15,100,1
 4510 REM IF state%=2 THEN SOUND 1,-10,50,5
 4520 =pBullet%+?(pBullet%+eSIZE)
 4530 REM --------------------------------------------------
 4540 DEF FN_InitAlien(type%, pEntity%, pImage%, state%, colour%, x%, y%, pathIndex%)
 4550 endAddress%=FN_InitEntity(type%, 1, pEntity%, pImage%, state%, colour%, x%, y%)
 4560 ?(pEntity%+eFLIGHT_PATH_INDEX)=pathIndex%
 4570 =endAddress%
 4580 REM --------------------------------------------------
 4590 DEF PROC_AlienHit(pAlien%, pBullet%)
 4600 PROC_DrawEntity(pAlien%, 0)
 4610 ?(pAlien%+eSTATE)=ALIEN_EXPLODE
 4620 !(pAlien%+eIMAGE)=pExplosionImage%
 4630 ?(pBullets%+eSTATE)=3
 4640 SOUND 0,-15,150,1
 4650 score%=score%+10
 4660 ENDPROC
 4670 REM --------------------------------------------------
 4680 DEF PROC_CheckAlienCollision(pAlien%, pBullets%, pExplosionImage%)
 4690 REM If alien is exploding (or dead) then ignore
 4700 cRadius%=?(!(pAlien%+eIMAGE)+2)
 4710 IF ?(pAlien%+eSTATE)<20 ENDPROC
 4720 FOR B=0 TO MaxBullets%
 4730   IF ?(pBullets%+eSTATE)>0 AND FN_IsCollision(workAlien%, pBullets%, cRadius%) PROC_AlienHit(pAlien%, pBullets%):ENDPROC
 4740   pBullets%=pBullets%+?(pBullets%+eSIZE)
 4750 NEXT B
 4760 ENDPROC
 4770 REM --------------------------------------------------
 4780 DEF FN_IsPlayerCollision(pRocket%, pBombs%)
 4790 cRadius%=?(!(pRocket%+eIMAGE)+2)
 4800 FOR B=0 TO MaxBombs%
 4810   IF ?(pBombs%+eSTATE)>0 AND FN_IsCollision(pRocket%, pBombs%, cRadius%) THEN ?(pBombs%+eSTATE)=3: =1
 4820   pBombs%=pBombs%+?(pBombs%+eSIZE)
 4830 NEXT B
 4840 =0
 4850 REM --------------------------------------------------
 4860 DEF FN_UpdateAlien(pAlien%, pBullets%, pFlightPath%, pExplosionImage%)
 4870 PROC_CheckAlienCollision(pAlien%, pBullets%, explosionImage%)
 4880 fpi%=?(pAlien%+eFLIGHT_PATH_INDEX)
 4890 fpi%=fpi%+1
 4900 IF fpi%>=FLIGHT_PATH_SIZE fpi%=0:PROC_MoveEntityTo(pAlien%,FLIGHT_PATH_IX, FLIGHT_PATH_IY)
 4910 ?(pAlien%+eFLIGHT_PATH_INDEX)=fpi%
 4920 pLookUp%=pFlightPath%+(fpi%*2)
 4930 dX=?(pLookUp%):IF dX>128 THEN dX=128-dX
 4940 dY=?(pLookUp%+1):IF dY>128 THEN dY=128-dY
 4950 =FN_MoveEntity(pAlien%, dX, dY)
 4960 REM --------------------------------------------------
 4970 DEF FN_DropBomb(pAlien%,pNextBomb%)
 4980 =FN_SetBullet(pNextBomb%,2,!(workAlien%+eXCENTRE),!(workAlien%+eYCENTRE))
 4990 REM --------------------------------------------------
 5000 DEF PROC_KillPlayer(pPlayer%, pExplosionImage%)
 5010 PROC_DrawEntity(pPlayer%, 0)
 5020 IF ?(pPlayer%+eSTATE)<PLAYER_LIVE THEN ENDPROC
 5030 ?(pPlayer%+eSTATE)=PLAYER_EXPLODE
 5040 !(pPlayer%+eIMAGE)=pExplosionImage%
 5050 PROC_DrawEntity(pPlayer%, ?(pPlayer%+eCOLOUR))
 5060 SOUND 0,-15,100,20
 5070 ENDPROC
 5080 REM --------------------------------------------------
 5090 DEF PROC_NewPlayer(pPlayer%, pImage%)
 5100 PROC_DrawEntity(pPlayer%, 0)
 5110 ?(pPlayer%+eSTATE)=PLAYER_LIVE
 5120 !(pPlayer%+eIMAGE)=pImage%
 5130 PROC_DrawEntity(pPlayer%, ?(pPlayer%+eCOLOUR))
 5140 ENDPROC
 5150 REM
 5160 REM --------------------------------------------------
 5170 REM Alien flight path functions
 5180 REM --------------------------------------------------
 5190 DEF FN_InitFlightPattern(address%)
 5200 FOR N=0 TO FLIGHT_PATH_SIZE
 5210   yBase=SIN(((N/4)+5)/7.8)
 5220   X=INT(yBase*18):IF X<0 THEN X=128-X
 5230   Y=INT(COS(yBase/0.4)*16):IF Y<0 THEN Y=128-Y
 5240   ?(address%)=X:?(address%+1)=Y
 5250   address%=address%+2
 5260 NEXT N
 5270 =address%
 5280 REM
 5290 DEF PROC_StartAlien(pAliens%)
 5300 pNext%=pAliens%
 5310 FOR A=0 TO MaxAliens%
 5320   IF ?(pNext%+eSTATE)=0 THEN pNext%=FN_InitAlien(eALIEN, pNext%, alien1Image%, ALIEN_LIVE, 1, FLIGHT_PATH_IX, FLIGHT_PATH_IY, FLIGHT_PATH_SIZE):ENDPROC
 5330   pNext%=FN_NextEntity(pNext%)
 5340 NEXT A
 5350 ENDPROC