add cheat for Twerps

res/history.md

@@ -12,7 +12,7 @@
 
  - Added help screen (press ? in search or browse mode to show)
  - Added global cheat mode (press Ctrl-C in search or browse mode to toggle)
- - Added 58 game cheats
+ - Added 59 game cheats
  - Fixed corrupted graphics in Asteroid Blaster
  - Fixed corrupted graphics in Sneakers game, demo, and screenshots, and now we are entirely done with this I promise
  - Fixed Axis Assassin demo hanging on IIgs

src/prelaunch/twerps.a

@@ -0,0 +1,32 @@
+;license:MIT
+;(c) 2019 by 4am
+
+!cpu 6502
+!to "build/PRELAUNCH/TWERPS",plain
+*=$106
+
+         !source "src/prelaunch/common.a"
+
+         +GET_MACHINE_STATUS
+         and   #CHEATS_ENABLED
+         sta   patch+1
+         ldx   #(end_patch-patch-1) ; copy patch code to zero page (stack will be destroyed by the time we need to patch)
+-        lda   patch,x
+         sta   $100-end_patch+patch,x
+         dex
+         bpl   -
+         lda   #($100-end_patch+patch)
+         sta   $1DF6
+         lda   #$00
+         sta   $1DF7
+         jmp   $1D97      ; decompress and show title
+patch
+         lda   #0         ; SMC
+         beq   +
+         lda   #$AD
+         sta   $0640      ; patch - don't decrease lives
+         sta   $0774      ; patch - don't decrease lives
+         sta   $0F05      ; patch - don't decrease lives
++
+         jmp   $0400
+end_patch