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Biker Babe Story
Naughty Toys
Name:
Biker Babe from Barbados |
Opening Screen Level One Cemetary Level Background Bitmap Objects Bitmap Runtime Document BikerBabe.s Misc.i ProPlay.i Map.i Back.i Title.i Sounds.i Death.i Babe.i Death.i Biker Babe
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Overview: I wrote Biker Babe one weekend as a testament to senseless violence in video games. A friend helped by composing the complementary music and by drawing some of the graphics. The overall tone and artistic impression came out exactly as I wanted. Ironically, I now believe video game violence needs to be monitored to prevent the desensitization to humanity. Game Design:
Biker Babe is a platform shooter with several levels. It is designed to be simple but absurd. To win, all you need to do is move Biker Babe to the far right end of each level while avoiding perverts, aliens, werewolves, and the typical male narcissist. The game is over when Biker Babe dies. That happens when she falls to an off screen location or gets way to close to an enemy. Game Development: The following is a detailed explanation of the key design choices I made while developing this game. The code snippets are taken from BikerBabe.s. [deleted code...] lea backname,a1 moveq #0,d0 CALLEXEC OpenLibrary tst.l d0 beq QUIT move.l d0,_BackBase move.l _BackBase,a6 moveq #1,d0 jsr -30(a6) tst.l d0 bne QU Games run best without the OS especially when the game reads and writes directly to the hardware devices. So, the OS is halted and a snapshot of the current state is recorded so it can be restored when the game exits. The BackStab library contains a routine to do this. So, let's use it! [deleted code...] SETUP move.w #32,$DFF1 When coding a game, I prefer PAL over NTSC because it gives more clock cycles during the vertical blank period - err... I mean, PAL allows more pretty smooth moving graphics than NTSC. [deleted code...] MOVECOP lea CList1,a1 move.l a1,$DFF080 move.w #$FFFF,$DFF088 move.w #$83C0,$DFF0 I cool feature of the Amiga is writing custom code for the Copper chip. My Copper list is used to create the pretty blue shaded background. However, one might use it to trace the raster as it is drawn in real time! [deleted code...] MAIN cmp.b #$45,Key beq QUIT cmp.w #195,BabeY bgt DEAD cmp.w #212,Distance bge S1ANIM jsr SHOOT jsr DOMAIN cmp.b #255,Help beq mn6 cmp.w #18,PervA bge mn5 move.w PervX,d0 move.w PervY,d1 sub.w BabeX,d0 bpl mn1 neg.w d0 mn1 sub.w BabeY,d1 bpl mn2 neg.w d1 mn2 add.w d0,d1 cmp.w #12,d1 ble TOUCH mn5 cmp.w #18,BervA bge mn6 move.w BervX,d0 move.w BervY,d1 sub.w BabeX,d0 bpl mn3 neg.w d0 mn3 sub.w BabeY,d1 bpl mn4 neg.w d1 mn4 add.w d0,d1 cmp.w #12,d1 ble TOUCH mn6 jmp MA This looks like a sloppy wrapper routine for the main routine, DOMAIN. This code iterates though all the possible ways which the game may end. End key pressed -Babe fell off screen - Level completed - Or, one of the two enemies got too close. [deleted code...] TOUCH move.w #45,Count move.w #3600,BabeD move.w #36,BabeA move.w #15,BabeS t1 jsr DOMAIN sub.w #1,BabeS bpl t2 move.w #6,BabeS add.w #1800,BabeD t2 sub.w #1,Count bpl You were touched by a pervert and the end animation needs to play before the game over is displayed. [deleted code...] DEAD cmp.w #9,Level bne de0 cmp.w #200,Distance bge THE We fell off the screen but if this is the last level and we are at the end, the game is won. [deleted code...] S1ANIM add.w #1,Lev The SxANIM routines are all in-game animation routines. [deleted code...] MVBACK btst.b #0,$DFF005 beq MVBACK mb0 cmp.b #$30,$DFF006 bne mb0 move.l _BitMapY,d1 move.l _BitMapN,d0 move.l d1,_BitMapN move.l d0,_BitMa If you swap buffers while the CRT is drawing the screen, a noticable rift will appear in your game screen. So, we wait for the raster to reach the vertical blanking period (The time after the screen is drawn but before the next time it is drawn). Then, we swap buffers. This is an ideal time to begin writing to the alternate buffer because the display hardware isn't controlling the bus. [deleted code...] ADDMAP move.w #1,d1 ap1 move.l a1,a3 move.l CurMap,a0 lea BackMap,a4 move.w BMapOff,d7 sub.w d1,d7 cmp.w #13,d7 bge ap5 cmp.w #0,d7 blt ap5 move.w Distance,d6 move.w BMapOff,d7 sub.w d1,d7 ap3 lea 64(a3,d6),a3 move.w d7,d0 mulu #2304,d0 lea 64(a3,d0),a3 lsr.w #1,d6 add.w d6,a0 lsl.w #7,d7 lea 64(a0,d7),a0 moveq #0,d0 move.b (a0)+,d0 divu #20,d0 swap d0 lsl.w #1,d0 add.w d0,a4 swap d0 mulu #720,d0 add.w d0,a4 moveq #4,d5 jsr BLTWAIT move.l #$FFFFFFFF,$DFF044 move.l #$0026007E,$DFF064 move.l #$09F00000,$DFF040 ap4 move.l a4,$DFF050 move.l a3,$DFF054 move.w #$0481,$DFF058 add.l #30000,a3 add.w #8000,a4 jsr BLTWAIT dbf d5,ap4 ap5 dbf d1,ap1 r The background is rendered using the classic tile technique. That is, tiles are taken from a source bitmap (The GetMap - see background image) and placed in the background during game play. We know what tile goes where because a data array (the LevMap) stores the tile arrangement. The code near BLTxxx annotation sets up the blitter hardware for an asyncronous data movement. [deleted code...] CLEANUP move.l _BitMapN,a5 add.l #158000,a5 move.l (a5)+,a0 jsr CLNDUDE cu2 move.l _BitMapN,a5 add.l #160000,a5 cb2 move.l (a5)+,a0 jsr CLNDUDE cb6 move.l _BitMapN,a5 add.l #156000,a5 move.l (a5),a0 move.l #0,(a5)+ jsr CLNDUDE cu8 move.l _BitMapN,a5 add.l #154000,a5 move.l (a5),a0 move.l #0,(a5 All moving characters are blits (as opposed to a sprite). So, we need to restore the background (which we saved previously) before we move the character. Sprites do not require these extra data movements but they have size, number, and color restrictions. [deleted code...] QUIT tst.l _BackBase beq q1 jsr mt_end move.l _BackBase,a6 jsr -36(a6) q1 tst.l _BckGrnd1 beq q2 move.l _BckGrnd1,a1 move.l #162000,d0 CALLEXEC FreeMem q2 tst.l _BckGrnd2 beq q3 move.l _BckGrnd2,a1 move.l #162000,d0 CALLEXEC FreeMem q3 move.l #0,d0 r Oh yeah, before halting the OS, we did request the memory we needed for the game. This prevents writing over data currently used by the OS which would prevent the OS from properly restarting. So, the memory is freed before the program is exits. [deleted code...] CList1 dc.w $102,$0000 dc.w $E0,$0000 dc.w $E2,$0000 dc.w $E4,$0000 dc.w $E6,$0000 dc.w $E8,$0000 dc.w $EA,$0000 dc.w $EC,$0000 dc.w $EE,$0000 dc.w $F0,$0000 dc.w $F2,$0000 dc.w $FFFF,$FFFE dc.w $1001,$FF00 dc.w $180,$000F dc.w $2001,$FF00 dc.w $180,$000E dc.w $3001,$FF00 dc.w $180,$000D dc.w $4001,$FF00 dc.w $180,$000C dc.w $5001,$FF00 dc.w $180,$000B dc.w $6001,$FF00 dc.w $180,$000A dc.w $7001,$FF00 dc.w $180,$0009 dc.w $8001,$FF00 dc.w $180,$0008 dc.w $9001,$FF00 dc.w $180,$0007 dc.w $A001,$FF00 dc.w $180,$0006 dc.w $B001,$FF00 dc.w $180,$0005 dc.w $C001,$FF00 dc.w $180,$0004 dc.w $D001,$FF00 dc.w $180,$0003 dc.w $E001,$FF00 dc.w $180,$0002 dc.w $F001,$FF00 dc.w $180,$0001 dc.w $FF01,$FF00 dc.w $180,$0000 dc.w $FFFF,$FF This is the copper list. It is a program executable by the copper chip. This is clearly one of the coolest features of the Amiga. This is what makes midscreen resolution/palette changes possible. |
A woman with a shotgun visually represents the playable character (Biker Babe). She has the ability to move left, right, jump or shoot and is affected by simulated gravity. Jumping is executed with a single button push. However, shooting requires two; the first cocks the gun and the second shoots. Animation is limited to a three-frame cycle for walking both right and left. Jumping requires one frame. Cocking the shotgun requires three-frames and halts player movement until complete.
The game utilizes Protracker mods for theme music and background music. A friend composed both of these awesome tracks. Thanks! The game wouldn't be the same without them!
