Give a turn for the enemies to turn around when bunny is behind them

7 files changed, 99 insertions, 7 deletions

diff --git a/Makefile b/Makefile
index a5010d5..2d843f5 100644
--- a/Makefile
+++ b/Makefile
@@ -8,7 +8,11 @@ tileset.gbasm: ./scripts/generate-tiledata.py $(wildcard ./sprites/**/* ./sprite
 %.gbasm: ./%.gbtxt ./scripts/generate_from_gbtxt.py
 	python ./scripts/generate_from_gbtxt.py $< > $@
 
-build/main.rom: main.gbasm tileset.gbasm text.gbasm dialogues/text.gbasm
+build/main.rom: build/main.rom.unsigned
+	cp build/main.rom.unsigned build/main.rom
+	python scripts/set_checksums.py build/main.rom
+
+build/main.rom.unsigned: main.gbasm tileset.gbasm text.gbasm dialogues/text.gbasm
 	mkdir -p build
 	gbasm $< $@ > build/main.sym
 
@@ -23,4 +27,4 @@ gearboy: build/main.rom
 	gearboy build/main.rom build/main.sym
 
 clean:
-	rm -rf build
+	rm -rf buil1
diff --git a/enemiesattacks/basic.gbasm b/enemiesattacks/basic.gbasm
index c617b7a..63bf3e4 100644
--- a/enemiesattacks/basic.gbasm
+++ b/enemiesattacks/basic.gbasm
@@ -1,5 +1,21 @@
 Basic_Enemy_Attack: ; Direction to face in E. Result in BC (XY), Direction in D
 	LD A, E
+	DEC A
+	DEC D
+	XOR D
+	INC D
+	CP $00
+	JR Z, =.attack
+	BIT 1, A
+	JR NZ, =.attack
+
+	LD A, E
+	OR $00
+	LD D, A
+	RET
+
+	.attack:
+	LD A, E
 	OR $10
 	LD D, A
 
diff --git a/enemiesattacks/freeze.gbasm b/enemiesattacks/freeze.gbasm
index eb27a48..35dadf3 100644
--- a/enemiesattacks/freeze.gbasm
+++ b/enemiesattacks/freeze.gbasm
@@ -1,5 +1,21 @@
 Freeze_Enemy_Attack: ; Direction to face in E. Result in BC (XY), Direction in D
 	LD A, E
+	DEC A
+	DEC D
+	XOR D
+	INC D
+	CP $00
+	JR Z, =.attack
+	BIT 1, A
+	JR NZ, =.attack
+
+	LD A, E
+	OR $00
+	LD D, A
+	RET
+
+	.attack:
+	LD A, E
 	OR $10
 	LD D, A
 
diff --git a/enemiesattacks/laser.gbasm b/enemiesattacks/laser.gbasm
index caf6db2..c26e4e3 100644
--- a/enemiesattacks/laser.gbasm
+++ b/enemiesattacks/laser.gbasm
@@ -1,4 +1,20 @@
 Laser_sight_check: ; BC = XY of the enemy. D is unchanged. Direction to face in E (or 0 if not)
+	LD A, E
+	DEC A
+	DEC D
+	XOR D
+	INC D
+	CP $00
+	JR Z, =.attack
+	BIT 1, A
+	JR NZ, =.attack
+
+	LD A, E
+	OR $00
+	LD D, A
+	RET
+
+	.attack:
 	LD E, $00
 
 	; straight line + distance <= 4
diff --git a/entity/list.gbasm b/entity/list.gbasm
index ff70248..f142505 100644
--- a/entity/list.gbasm
+++ b/entity/list.gbasm
@@ -151,7 +151,7 @@ Entity_list:
 		.DB $05
 
 		; Interaction Jump Table index
-		.DB $01
+		.DB $02
 
 		; Starting health
 		.DB $00
diff --git a/init.gbasm b/init.gbasm
index e3296de..e4706e9 100644
--- a/init.gbasm
+++ b/init.gbasm
@@ -13,15 +13,31 @@ Start:
 	JP =Initialize_RAM
 
 .PADTO 0x0104
-Nintendo_Logo: ; The Nintendo logo must be stored in bytes 0x104-133
+Header:
+.Nintendo_Logo: ; The Nintendo logo must be stored in bytes 0x104-133
 	.DB $CE,$ED,$66,$66,$CC,$0D,$00,$0B,$03,$73,$00,$83,$00,$0C,$00,$0D
 	.DB $00,$08,$11,$1F,$88,$89,$00,$0E,$DC,$CC,$6E,$E6,$DD,$DD,$D9,$99
 	.DB $BB,$BB,$67,$63,$6E,$0E,$EC,$CC,$DD,$DC,$99,$9F,$BB,$B9,$33,$3E
 
 .PADTO 0x0134
-Checksum: ; The bytes 0x134-0x14d need to add up to 0xe7 (= 0xff - 0x19)
-	.DB $00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
-	.DB $00,$00,$00,$00,$00,$00,$00,$00,$00,$e7
+
+.Title:
+.PADTO 0x13f
+
+.Manufacturer_code:
+.PADTO 0x142
+
+.CGB_Flag: .DB $69
+.Licensee_code_new: .DB $00, $00
+.SGB_Flag: .DB $00
+.MBC: .DB $01
+.ROM_size: .DB $00
+.RAM_size: .DB $00 ; The .sav cartridge kind of ram
+.Destination_code: .DB $01 ; Overseas
+.Licensee_code_old: .DB $00
+.Version_number: .DB $42
+.Header_checksum: .DB $00 ; Will be set after assembly by build scripts
+.Global_checksum: .DB $00, $00 ; Will be set after assembly by build scripts
 
 Initialize_RAM:
 ; Disable Interrupts
diff --git a/scripts/set_checksums.py b/scripts/set_checksums.py
new file mode 100644
index 0000000..e05d1cf
--- /dev/null
+++ b/scripts/set_checksums.py
@@ -0,0 +1,24 @@
+import sys
+
+if len(sys.argv) != 2:
+    raise ValueError("Rom file must be specified as first argument")
+
+rom_filename = sys.argv[1]
+
+rom_file = open(rom_filename, 'r+b')
+
+rom_file.seek(0x0134)
+
+header = rom_file.read(0x19)
+
+header_checksum = 0
+for b in header:
+    header_checksum = (header_checksum - int(b) - 1) & 0xff
+
+print("HEADER CHECKSUM =", hex(header_checksum), file=sys.stderr)
+
+rom_file.seek(0x014d)
+
+rom_file.write(bytes(bytearray([header_checksum])))
+
+rom_file.close()