From 5199df364ae8860ee4dbb8fba3b62fddb0ba801f Mon Sep 17 00:00:00 2001
From: Sebastian Riedel <git@basxto.de>
Date: Fri, 4 Feb 2022 02:07:03 +0100
Subject: [PATCH 01/10] Switch to makebin

---
 game/makefile            |   3 +-
 ihx2gb/ihx2gb.js         | 257 ---------------------------------------
 ihx2gb/package-lock.json |  26 ----
 ihx2gb/package.json      |  10 --
 4 files changed, 2 insertions(+), 294 deletions(-)
 delete mode 100644 ihx2gb/ihx2gb.js
 delete mode 100644 ihx2gb/package-lock.json
 delete mode 100644 ihx2gb/package.json

diff --git a/game/makefile b/game/makefile
index fe32ea9..27e66c0 100644
--- a/game/makefile
+++ b/game/makefile
@@ -1,5 +1,6 @@
 CC = sdcc
 ASMC = sdasgb
+MKROM = makebin
 CFLAGS = -c -mgbz80
 ASMFLAGS = -plosgffjw
 LINKFLAGS = -mgbz80 --no-std-crt0 --data-loc 0xc0a0
@@ -36,7 +37,7 @@ obj/dependencies: $(SRCFILES)
 
 bin/BubbleFactory.gb: obj/game.ihx
 	@mkdir -p bin
-	node ../ihx2gb --name BUBBLEFACT --licensee DH --cartridge 0x1B --ram 1 --version 1 $< $@
+	$(MKROM) -Z -yn BUBBLEFACT -yk DH -yt 0x1B -ya 1 -yS -yp0x014C=1 $< $@
 
 obj/game.ihx: $(OBJFILES)
 	@mkdir -p obj
diff --git a/ihx2gb/ihx2gb.js b/ihx2gb/ihx2gb.js
deleted file mode 100644
index 7445dc9..0000000
--- a/ihx2gb/ihx2gb.js
+++ /dev/null
@@ -1,257 +0,0 @@
-"use strict";
-
-const fs = require("fs");
-const path = require("path");
-const commander = require("commander");
-const Overflow = require("overflow-js").Overflow;
-
-function parseHexPair(string, index) {
-  return parseInt(string.substr(index, 2), 16);
-}
-
-function writeLogo(buffer) {
-  const logoBuffer = Buffer.from([
-    0xCE, 0xED, 0x66, 0x66, 0xCC, 0x0D, 0x00, 0x0B, 0x03, 0x73, 0x00, 0x83, 0x00, 0x0C, 0x00, 0x0D,
-    0x00, 0x08, 0x11, 0x1F, 0x88, 0x89, 0x00, 0x0E, 0xDC, 0xCC, 0x6E, 0xE6, 0xDD, 0xDD, 0xD9, 0x99,
-    0xBB, 0xBB, 0x67, 0x63, 0x6E, 0x0E, 0xEC, 0xCC, 0xDD, 0xDC, 0x99, 0x9F, 0xBB, 0xB9, 0x33, 0x3E
-  ]);
-  
-  logoBuffer.copy(buffer, 0x0104);
-}
-
-function writeTitle(buffer, title) {
-  if(title.length > 11) {
-    console.warn(`warning: title longer than 11 characters, later characters will be ignored`);
-  }
-  
-  if(/^[A-Z0-9 ]*$/g.test(title) == false) {
-    console.error("title may only have uppercase letters, digits, and spaces");
-    process.exit(1);
-  }
-  
-  const startAddress = 0x0134;
-  buffer.fill(0x00, startAddress, startAddress + 11);
-  buffer.write(title, startAddress, Math.min(title.length, 11), "ascii");
-}
-
-function writeManufacturerCode(buffer, code) {
-  if(code.length > 4) {
-    console.warn(`warning: manufacturer code longer than 4 characters, later characters will be ignored`);
-  }
-  
-  if(/^[A-Z0-9 ]*$/g.test(code) == false) {
-    console.error("manufacturer code may only have uppercase letters, digits, and spaces");
-    process.exit(1);
-  }
-  
-  const startAddress = 0x013F;
-  buffer.fill(0x00, startAddress, startAddress + 4);
-  buffer.write(code, startAddress, Math.min(code.length, 4), "ascii");
-}
-
-function writeCGBFlag(buffer, flag) {
-  buffer.writeUInt8(flag, 0x0143);
-}
-
-function writeLicenseeCode(buffer, code) {
-  if(code.length > 2) {
-    console.warn(`warning: licensee code longer than 2 characters, later characters will be ignored`);
-  }
-  
-  if(/^[a-zA-Z0-9 ]*$/g.test(code) == false) {
-    console.error("licensee code may only have letters, digits, and spaces");
-    process.exit(1);
-  }
-  
-  const startAddress = 0x0144;
-  buffer.fill(0xFF, startAddress, startAddress + 2);
-  buffer.write(code, startAddress, Math.min(code.length, 2), "ascii");
-}
-
-function writeSGBFlag(buffer, flag) {
-  buffer.writeUInt8(flag, 0x0146);
-}
-
-function writeCartridgeType(buffer, type) {
-  buffer.writeUInt8(type, 0x0147);
-}
-
-function writeROMSize(buffer, size) {
-  buffer.writeUInt8(size, 0x0148);
-}
-
-function writeRAMSize(buffer, size) {
-  buffer.writeUInt8(size, 0x0149);
-}
-
-function writeDestinationCode(buffer, code) {
-  buffer.writeUInt8(code, 0x014A);
-}
-
-function writeOldLicenseeCode(buffer, code) {
-  buffer.writeUInt8(code, 0x014B);
-}
-
-function writeROMVersion(buffer, version) {
-  buffer.writeUInt8(version, 0x014C);
-}
-
-function writeHeaderChecksum(buffer) {
-  let x = Overflow.ubyte(0);
-  for(let index = 0x0134; index <= 0x014C; index++) {
-    x = x.minus(buffer[index]).minus(1);
-  }
-  buffer.writeUInt8(x.value, 0x014D);
-}
-
-function writeROMChecksum(buffer) {
-  let x = Overflow.ushort(0);
-  for(let index = 0x00; index < buffer.length; index++) {
-    if(index == 0x014E || index == 0x014F) {
-      continue;
-    }
-    x = x.plus(buffer[index]);
-  }
-  buffer.writeUInt16BE(x.value, 0x014E);
-}
-
-function processMap(mapFilePath, symOutputPath) {
-  if(fs.existsSync(mapFilePath) == false) {
-    return;
-  }
-  
-  const regex = /^[\s]+([0-9A-F]{8})  _([a-zA-Z0-9_]+)/;
-  
-  const text = fs.readFileSync(mapFilePath, "utf8");
-  const lines = text.split(/[\n\r]+/g);
-  const addresses = [];
-  lines.forEach((line) => {
-    const match = regex.exec(line);
-    if(match == null) {
-      return;
-    }
-    const address = match[1];
-    const symbol = match[2];
-    
-    addresses.push({
-      "address" : address,
-      "symbol" : symbol
-    });
-  });
-  
-  const symbolLines = [
-    "; Generated by IHX2GB",
-    ""
-  ];
-  addresses.forEach((address) => {
-    symbolLines.push(`00:${address.address.substr(4)} ${address.symbol}`);
-  });
-  
-  fs.writeFileSync(symOutputFilePath, symbolLines.join("\n"));
-}
-
-commander
-  .usage("[options] <in_file> <out_file>")
-  .option("-n, --name [value]", "The name in the header. Default: \"MY GAME\"", "MY GAME")
-  .option("-m, --manufacturer [code]", "The manufacturer code. Default: \"\"", "")
-  .option("-c, --cgb [flag]", "The decimal Game Boy Color support flag. 128 for CGB+GB, 192 for CGB-only. Default: 0", "0", parseInt)
-  .option("-l, --licensee [code]", "The ASCII licensee code. Default: \"00\"", "00")
-  .option("-s, --sgb [flag]", "The decimal Super Game Boy support flag. 3 to enable. Default: 0", "0", parseInt)
-  .option("-t, --cartridge [type]", "The decimal cartridge type. Default: 0", "0", parseInt)
-  .option("-r, --rom [code]", "The decimal ROM size code. File will be 32KB << value, except for 82, 83, and 84. Default: 0", "0", parseInt)
-  .option("-a, --ram [code]", "The decimal external RAM size code. Default: 0", "0", parseInt)
-  .option("-d, --destination [code]", "The destination code. 0 for Japan, 1 for international. Default: 1", "1", parseInt)
-  .option("--oldlicensee [code]", "The decimal old licensee code. 51 to use new licensee code. SGB will not work if != 51. Default: 51", "51", parseInt)
-  .option("-v, --version [version]", "The ROM version. Default: 0", "0", parseInt)
-
-commander.on("--help", () => {
-  console.log("Go to http://gbdev.gg8.se/wiki/articles/The_Cartridge_Header for header details, including values for Cartridge Type, ROM Size, and RAM Size. That site lists codes in hex, but must be provided here in decimal.");
-  console.log("");
-});
-
-commander.parse(process.argv);
-
-if(commander.rom > 8) {
-  let n = 32768;
-  for(let i=0; i < commander.rom; i++) {
-    n *= 2;
-  }
-  console.error("rom size codes > 8 unsupported. Fun fact, you asked me to make a file " + (n) + " bytes big! Wow!");
-  process.exit(1);
-}
-
-if(commander.args.length != 2) {
-  console.error("must provide both an input and output file");
-  process.exit(1);
-}
-
-const inputFilePath = path.resolve(commander.args[0]);
-const outputFilePath = path.resolve(commander.args[1]);
-
-const inputFileDirectory = path.dirname(inputFilePath);
-const inputFileBasename = path.basename(inputFilePath, path.extname(inputFilePath));
-const mapFilePath = path.join(inputFileDirectory, inputFileBasename + ".map");
-
-const outputFileDirectory = path.dirname(outputFilePath);
-const outputFileBasename = path.basename(outputFilePath, path.extname(outputFilePath));
-const symOutputFilePath = path.join(outputFileDirectory, outputFileBasename + ".sym");
-
-processMap(mapFilePath, symOutputFilePath);
-
-const ihxText = fs.readFileSync(inputFilePath, { "encoding" : "utf8" });
-const ihxRecords = ihxText.split(/[\n\r]+/g).filter((record) => { return record.length > 0; });
-const gbBuffer = Buffer.alloc(32768 << commander.rom, 0xFF);
-
-let baseAddress = 0;
-
-ihxRecords.forEach((record) => {
-  let head = 0;
-  
-  if(record[head] != ":") {
-    console.error("not an ihx file");
-    process.exit(1);
-  }
-  
-  head +=1;
-  
-  const dataLength = parseHexPair(record, head);
-  head += 2;
-  
-  const address = baseAddress + (parseHexPair(record, head) << 8) + parseHexPair(record, head + 2);
-  head += 4;
-  
-  const type = parseHexPair(record, head);
-  head += 2;
-  
-  if(type == 0) {
-    // Data Record, copy bytes
-    for(let index = 0; index < dataLength; index++) {
-      const byte = parseHexPair(record, head);
-      head += 2;
-      
-      gbBuffer[address + index] = byte;
-    }
-  } else if(type == 1) {
-    // EOF Record.
-  } else {
-    console.error("unsupported record type");
-    process.exit(1);
-  }
-});
-
-writeLogo(gbBuffer);
-writeTitle(gbBuffer, commander.name);
-writeManufacturerCode(gbBuffer, commander.manufacturer);
-writeCGBFlag(gbBuffer, commander.cgb);
-writeLicenseeCode(gbBuffer, commander.licensee);
-writeSGBFlag(gbBuffer, commander.sgb);
-writeCartridgeType(gbBuffer, commander.cartridge);
-writeROMSize(gbBuffer, commander.rom);
-writeRAMSize(gbBuffer, commander.ram);
-writeDestinationCode(gbBuffer, commander.destination);
-writeOldLicenseeCode(gbBuffer, commander.oldlicensee);
-writeROMVersion(gbBuffer, commander.version);
-writeHeaderChecksum(gbBuffer);
-writeROMChecksum(gbBuffer);
-
-fs.writeFileSync(outputFilePath, gbBuffer);
diff --git a/ihx2gb/package-lock.json b/ihx2gb/package-lock.json
deleted file mode 100644
index 78345e8..0000000
--- a/ihx2gb/package-lock.json
+++ /dev/null
@@ -1,26 +0,0 @@
-{
-  "name": "ihx2gb",
-  "version": "0.0.0",
-  "lockfileVersion": 1,
-  "requires": true,
-  "dependencies": {
-    "commander": {
-      "version": "2.9.0",
-      "resolved": "https://registry.npmjs.org/commander/-/commander-2.9.0.tgz",
-      "integrity": "sha1-nJkJQXbhIkDLItbFFGCYQA/g99Q=",
-      "requires": {
-        "graceful-readlink": ">= 1.0.0"
-      }
-    },
-    "graceful-readlink": {
-      "version": "1.0.1",
-      "resolved": "https://registry.npmjs.org/graceful-readlink/-/graceful-readlink-1.0.1.tgz",
-      "integrity": "sha1-TK+tdrxi8C+gObL5Tpo906ORpyU="
-    },
-    "overflow-js": {
-      "version": "1.0.0",
-      "resolved": "https://registry.npmjs.org/overflow-js/-/overflow-js-1.0.0.tgz",
-      "integrity": "sha1-G8S//0Qg5Rc5ZuvWd8SASR7phPA="
-    }
-  }
-}
diff --git a/ihx2gb/package.json b/ihx2gb/package.json
deleted file mode 100644
index 2aa81c8..0000000
--- a/ihx2gb/package.json
+++ /dev/null
@@ -1,10 +0,0 @@
-{
-  "name": "ihx2gb",
-  "description": "converts intel ihx files to game boy format",
-  "version": "0.0.0",
-  "main": "ihx2gb",
-  "dependencies": {
-    "commander": "~2.9.0",
-    "overflow-js": "~1.0.0"
-  }
-}

From ead33fcd4d74b5b716450dd92c0e1ce4604b5e1e Mon Sep 17 00:00:00 2001
From: Sebastian Riedel <git@basxto.de>
Date: Fri, 4 Feb 2022 16:25:57 +0100
Subject: [PATCH 02/10] Update README and improve makefile

---
 README.md                 |  5 +++--
 game/makefile             | 37 +++++++++++++++++++++----------------
 img2gb/package-lock.json  |  2 +-
 makefile                  | 19 +++++++++++++++++++
 stringc/package-lock.json |  2 +-
 5 files changed, 45 insertions(+), 20 deletions(-)
 create mode 100644 makefile

diff --git a/README.md b/README.md
index 6c8da4f..2794362 100644
--- a/README.md
+++ b/README.md
@@ -9,11 +9,12 @@ I built this project on macOS. The instructions should be pretty easy to follow
 The build pipeline has dependencies on [node.js](http://nodejs.org) and [SDCC](http://sdcc.sourceforge.net). You'll need to install them.
 
 ### Dependencies
-`cd` into `ihx2gb/` and run `npm install`.
-
 `cd` into `img2gb/` and run `npm install`.
 
 `cd` into `stringc/` and run `npm install`.
 
 ### Building the Game
 `cd` into `game/` and run `make` or `make debug`.
+
+### Building the Game and Dependencies
+Just run `make`, `make debug` or `make run` in the root folder.
\ No newline at end of file
diff --git a/game/makefile b/game/makefile
index 27e66c0..2799cdd 100644
--- a/game/makefile
+++ b/game/makefile
@@ -1,6 +1,8 @@
 CC = sdcc
 ASMC = sdasgb
 MKROM = makebin
+EMU = sameboy
+NODE = node
 CFLAGS = -c -mgbz80
 ASMFLAGS = -plosgffjw
 LINKFLAGS = -mgbz80 --no-std-crt0 --data-loc 0xc0a0
@@ -14,44 +16,47 @@ OBJS = $(SRCS:.c=.o)
 SRCFILES = $(patsubst %.c,src/%.c,$(SRCS))
 OBJFILES = $(patsubst %.s,obj/%.rel,$(ASMS)) $(patsubst %.c,obj/%.rel,$(SRCS))
 
+.PHONY: build debug run clean
+
 build: obj/dependencies bin/BubbleFactory.gb
 
 debug: CFLAGS += -DDEBUG
 debug: build
 
 src/data_strings.c: data/strings.json 
-	node ../stringc data/stringsMap.json $< $@
+	$(NODE) ../stringc data/stringsMap.json $< $@
 
 src/data_gfx_%.c: data/gfx/%.png
-	node ../img2gb -n $(notdir $(basename $<)) $< $@
+	$(NODE) ../img2gb -n $(notdir $(basename $<)) $< $@
 
-obj/dependencies: $(SRCFILES)
+obj/dependencies: $(SRCFILES) | obj/
 	@echo "regenerate dependency file"
-	@mkdir -p obj
-	@rm -f obj/dependencies
+	@$(RM) -f obj/dependencies
 	@for srcFile in $(SRCFILES) ; do \
 		{ printf "obj/"; $(CC) -MM $$srcFile; } >> obj/dependencies ; \
 	done
 
 -include obj/dependencies
 
-bin/BubbleFactory.gb: obj/game.ihx
-	@mkdir -p bin
+bin/BubbleFactory.gb: obj/game.ihx | bin/
 	$(MKROM) -Z -yn BUBBLEFACT -yk DH -yt 0x1B -ya 1 -yS -yp0x014C=1 $< $@
 
-obj/game.ihx: $(OBJFILES)
-	@mkdir -p obj
+obj/game.ihx: $(OBJFILES) | obj/
 	$(CC) $(LINKFLAGS) $^ -o $@
 
-obj/%.rel: src/%.c
-	@mkdir -p obj
+obj/%.rel: src/%.c | obj/
 	$(CC) $(CFLAGS) $< -o $@
 
-obj/%.rel: src/%.s
-	@mkdir -p obj
+obj/%.rel: src/%.s | obj/
 	$(ASMC) $(ASMFLAGS) $@ $<
 
+%/:
+	@mkdir -p $@
+
+run: build
+	$(EMU) bin/BubbleFactory.gb
+
 clean:
-	rm -rf src/data_*
-	rm -rf obj
-	rm -rf bin
+	$(RM) -rf src/data_*
+	$(RM) -rf obj
+	$(RM) -rf bin
diff --git a/img2gb/package-lock.json b/img2gb/package-lock.json
index 1995d27..f1f5bd5 100644
--- a/img2gb/package-lock.json
+++ b/img2gb/package-lock.json
@@ -1,7 +1,7 @@
 {
   "name": "img2gb",
   "version": "0.0.0",
-  "lockfileVersion": 1,
+  "lockfileVersion": 2,
   "requires": true,
   "dependencies": {
     "commander": {
diff --git a/makefile b/makefile
new file mode 100644
index 0000000..4648552
--- /dev/null
+++ b/makefile
@@ -0,0 +1,19 @@
+.PHONY: build debug tools run clean
+
+build: tools
+	$(MAKE) -C game/ $@
+
+debug: tools
+	$(MAKE) -C game/ $@
+
+run: tools
+	$(MAKE) -C game/ $@
+
+clean:
+	$(MAKE) -C game/ $@
+	$(RM) -rf img2gb/node_modules stringc/node_modules
+
+tools: img2gb/node_modules stringc/node_modules
+
+%/node_modules:
+	cd $* && npm install
\ No newline at end of file
diff --git a/stringc/package-lock.json b/stringc/package-lock.json
index 64f85c0..900a929 100644
--- a/stringc/package-lock.json
+++ b/stringc/package-lock.json
@@ -1,7 +1,7 @@
 {
   "name": "stringc",
   "version": "1.0.0",
-  "lockfileVersion": 1,
+  "lockfileVersion": 2,
   "requires": true,
   "dependencies": {
     "commander": {

From ca4bd2e455d243bf7d3532088a74809cc73d4962 Mon Sep 17 00:00:00 2001
From: Sebastian Riedel <git@basxto.de>
Date: Fri, 4 Feb 2022 17:25:01 +0100
Subject: [PATCH 03/10] Allow custom SDCC paths

---
 README.md     | 9 ++++++++-
 game/makefile | 7 ++++---
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index 2794362..3cc26e5 100644
--- a/README.md
+++ b/README.md
@@ -17,4 +17,11 @@ The build pipeline has dependencies on [node.js](http://nodejs.org) and [SDCC](h
 `cd` into `game/` and run `make` or `make debug`.
 
 ### Building the Game and Dependencies
-Just run `make`, `make debug` or `make run` in the root folder.
\ No newline at end of file
+Just run `make`, `make debug` or `make run` in the root folder.
+
+### Building with an SDCC Snapshot
+*This is for versions of SDCC that aren't installed*
+```
+SDCC_HOME=/path/to/sdcc/share/sdcc/
+make SDCCBIN=${SDCC_HOME}../../bin/
+```
\ No newline at end of file
diff --git a/game/makefile b/game/makefile
index 2799cdd..7cf218c 100644
--- a/game/makefile
+++ b/game/makefile
@@ -1,6 +1,7 @@
-CC = sdcc
-ASMC = sdasgb
-MKROM = makebin
+SDCCBIN = 
+CC = $(SDCCBIN)sdcc
+ASMC = $(SDCCBIN)sdasgb
+MKROM = $(SDCCBIN)makebin
 EMU = sameboy
 NODE = node
 CFLAGS = -c -mgbz80

From a8d36235ac88ae454004630573c5ca24b8ad3612 Mon Sep 17 00:00:00 2001
From: Sebastian Riedel <git@basxto.de>
Date: Fri, 4 Feb 2022 18:51:09 +0100
Subject: [PATCH 04/10] Adapt to target renaming gbz80->sm83

---
 game/makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/game/makefile b/game/makefile
index 7cf218c..d322d17 100644
--- a/game/makefile
+++ b/game/makefile
@@ -4,9 +4,9 @@ ASMC = $(SDCCBIN)sdasgb
 MKROM = $(SDCCBIN)makebin
 EMU = sameboy
 NODE = node
-CFLAGS = -c -mgbz80
+CFLAGS = -c -msm83
 ASMFLAGS = -plosgffjw
-LINKFLAGS = -mgbz80 --no-std-crt0 --data-loc 0xc0a0
+LINKFLAGS = -msm83 --no-std-crt0 --data-loc 0xc0a0
 
 GFXS = $(notdir $(shell find data/gfx -name '*.png'))
 GFXSRC = $(patsubst %.png,data_gfx_%.c,$(GFXS))

From 5564c334156c81c29b007f3dabd21927f70173db Mon Sep 17 00:00:00 2001
From: Sebastian Riedel <git@basxto.de>
Date: Fri, 4 Feb 2022 19:06:40 +0100
Subject: [PATCH 05/10] Force old calling convention for handwritten asm

---
 game/src/gb.c      | 14 +++++++-------
 game/src/gb.h      | 14 +++++++-------
 game/src/memory.c  |  2 +-
 game/src/memory.h  |  2 +-
 game/src/sprites.c |  2 +-
 game/src/sprites.h |  2 +-
 6 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/game/src/gb.c b/game/src/gb.c
index f18892e..a887eaa 100644
--- a/game/src/gb.c
+++ b/game/src/gb.c
@@ -16,7 +16,7 @@ GBJoypadState gbJoypadReleasedSinceLastUpdate;
 // ===
 // Public API
 // ===
-void gbLCDDisable() {
+void gbLCDDisable() __sdcccall(0) {
     __asm
     
     push af
@@ -36,28 +36,28 @@ void gbLCDDisable() {
     __endasm;
 }
 
-void gbLCDEnable() {
+void gbLCDEnable() __sdcccall(0) {
     __asm
     ld hl, #0xff40
     set #7, (hl)
     __endasm;
 }
 
-void gbSpritesDisable() {
+void gbSpritesDisable() __sdcccall(0) {
     __asm
     ld hl, #0xff40
     res #1, (hl)
     __endasm;
 }
 
-void gbSpritesEnable() {
+void gbSpritesEnable() __sdcccall(0) {
     __asm
     ld hl, #0xff40
     set #1, (hl)
     __endasm;
 }
 
-void gbJoypadStateUpdate() {
+void gbJoypadStateUpdate() __sdcccall(0) {
     GBUInt8 lastValue;
     
     lastValue = gbJoypadState;
@@ -109,7 +109,7 @@ void gbJoypadStateUpdate() {
     gbJoypadReleasedSinceLastUpdate = (gbJoypadState ^ lastValue) & lastValue;
 }
 
-void gbLogUInt8(GBUInt8 value) {
+void gbLogUInt8(GBUInt8 value) __sdcccall(0) {
     (void)(value); // Suppresses unused variable warning
     
     __asm
@@ -128,7 +128,7 @@ void gbLogUInt8(GBUInt8 value) {
     __endasm;
 }
 
-void gbLogUInt16(GBUInt16 value) {
+void gbLogUInt16(GBUInt16 value) __sdcccall(0) {
     (void)(value); // Suppresses unused variable warning
     
     __asm
diff --git a/game/src/gb.h b/game/src/gb.h
index 39cb73a..fe62261 100644
--- a/game/src/gb.h
+++ b/game/src/gb.h
@@ -79,15 +79,15 @@ extern GBJoypadState gbJoypadState;
 extern GBJoypadState gbJoypadPressedSinceLastUpdate;
 extern GBJoypadState gbJoypadReleasedSinceLastUpdate;
 
-void gbLCDDisable();
-void gbLCDEnable();
+void gbLCDDisable() __sdcccall(0);
+void gbLCDEnable() __sdcccall(0);
 
-void gbSpritesDisable();
-void gbSpritesEnable();
+void gbSpritesDisable() __sdcccall(0);
+void gbSpritesEnable() __sdcccall(0);
 
-void gbJoypadStateUpdate();
+void gbJoypadStateUpdate() __sdcccall(0);
 
-void gbLogUInt8(GBUInt8 value);
-void gbLogUInt16(GBUInt16 value);
+void gbLogUInt8(GBUInt8 value) __sdcccall(0);
+void gbLogUInt16(GBUInt16 value) __sdcccall(0);
 
 #endif /* gb_h */
diff --git a/game/src/memory.c b/game/src/memory.c
index d8db993..76d6290 100644
--- a/game/src/memory.c
+++ b/game/src/memory.c
@@ -4,7 +4,7 @@ volatile const void * memoryCopySourceAddress;
 volatile void * memoryCopyDestinationAddress;
 volatile GBUInt8 memoryCopyLength;
 
-void memoryCopy() {
+void memoryCopy() __sdcccall(0) {
     __asm
     
     push af
diff --git a/game/src/memory.h b/game/src/memory.h
index db800fc..25b4d67 100644
--- a/game/src/memory.h
+++ b/game/src/memory.h
@@ -7,6 +7,6 @@ extern volatile const void * memoryCopySourceAddress;
 extern volatile void * memoryCopyDestinationAddress;
 extern volatile GBUInt8 memoryCopyLength;
 
-void memoryCopy();
+void memoryCopy() __sdcccall(0);
 
 #endif
diff --git a/game/src/sprites.c b/game/src/sprites.c
index d4c446c..a8b0bd8 100644
--- a/game/src/sprites.c
+++ b/game/src/sprites.c
@@ -35,7 +35,7 @@ void spritesInit() {
     tempAnimationPhase = 0;
 }
 
-void spritesWriteToOAM() {
+void spritesWriteToOAM() __sdcccall(0) {
     __asm
     call #0xFF80
     __endasm;
diff --git a/game/src/sprites.h b/game/src/sprites.h
index 149ba12..6cac954 100644
--- a/game/src/sprites.h
+++ b/game/src/sprites.h
@@ -38,7 +38,7 @@ extern volatile const SpriteFrameAttributes * spritesWriteAttributes;
 #define spritesAttributesMake(priority, flipX, flipY, paletteNumber) (((priority) << 7) | ((flipX) << 5) | ((flipY) << 6) | ((paletteNumber) << 4))
 
 void spritesInit();
-void spritesWriteToOAM();
+void spritesWriteToOAM() __sdcccall(0);
 void spritesWrite2x2();
 void spritesWrite1x1();
 

From 8b6b5402699e252db09e9d4e4749ae115d41d818 Mon Sep 17 00:00:00 2001
From: Sebastian Riedel <git@basxto.de>
Date: Fri, 4 Feb 2022 19:50:21 +0100
Subject: [PATCH 06/10] Add more debug flags and statistic tools

---
 game/makefile | 36 ++++++++++++++++++++++++++----------
 1 file changed, 26 insertions(+), 10 deletions(-)

diff --git a/game/makefile b/game/makefile
index 7cf218c..2fd6471 100644
--- a/game/makefile
+++ b/game/makefile
@@ -1,12 +1,15 @@
 SDCCBIN = 
 CC = $(SDCCBIN)sdcc
-ASMC = $(SDCCBIN)sdasgb
+AS = $(SDCCBIN)sdasgb
 MKROM = $(SDCCBIN)makebin
+# https://github.com/LIJI32/SameBoy or any other emulator
 EMU = sameboy
+# https://github.com/bbbbbr/romusage
+ROMUSE = romusage
 NODE = node
 CFLAGS = -c -mgbz80
-ASMFLAGS = -plosgffjw
-LINKFLAGS = -mgbz80 --no-std-crt0 --data-loc 0xc0a0
+ASFLAGS = -plosgffjw
+LDFLAGS = -mgbz80 --no-std-crt0 --data-loc 0xc0a0
 
 GFXS = $(notdir $(shell find data/gfx -name '*.png'))
 GFXSRC = $(patsubst %.png,data_gfx_%.c,$(GFXS))
@@ -17,11 +20,14 @@ OBJS = $(SRCS:.c=.o)
 SRCFILES = $(patsubst %.c,src/%.c,$(SRCS))
 OBJFILES = $(patsubst %.s,obj/%.rel,$(ASMS)) $(patsubst %.c,obj/%.rel,$(SRCS))
 
-.PHONY: build debug run clean
+ROM = BubbleFactory
 
-build: obj/dependencies bin/BubbleFactory.gb
+.PHONY: build debug run clean spaceleft statistics
 
-debug: CFLAGS += -DDEBUG
+build: obj/dependencies bin/$(ROM).gb
+
+debug: CFLAGS += -DDEBUG --debug
+debug: LDFLAGS += -Wl-y
 debug: build
 
 src/data_strings.c: data/strings.json 
@@ -39,23 +45,33 @@ obj/dependencies: $(SRCFILES) | obj/
 
 -include obj/dependencies
 
-bin/BubbleFactory.gb: obj/game.ihx | bin/
+bin/$(ROM).gb: obj/game.ihx | bin/
 	$(MKROM) -Z -yn BUBBLEFACT -yk DH -yt 0x1B -ya 1 -yS -yp0x014C=1 $< $@
+	cp obj/game.sym bin/$(ROM).sym
+	cp obj/game.noi bin/$(ROM).noi
+	test -e obj/game.cdb && cp obj/game.cdb bin/$(ROM).cdb
 
 obj/game.ihx: $(OBJFILES) | obj/
-	$(CC) $(LINKFLAGS) $^ -o $@
+	$(CC) $(LDFLAGS) $^ -o $@
 
 obj/%.rel: src/%.c | obj/
 	$(CC) $(CFLAGS) $< -o $@
 
 obj/%.rel: src/%.s | obj/
-	$(ASMC) $(ASMFLAGS) $@ $<
+	$(AS) $(ASFLAGS) $@ $<
 
 %/:
 	@mkdir -p $@
 
+spaceleft: build
+	$(ROMUSE) bin/$(ROM).noi -g -E
+
+statistics: build
+	test -e bin/$(ROM).cdb && $(ROMUSE) bin/$(ROM).cdb -g
+	$(ROMUSE) bin/$(ROM).noi -G -E -sH -a
+
 run: build
-	$(EMU) bin/BubbleFactory.gb
+	$(EMU) $(ROM)
 
 clean:
 	$(RM) -rf src/data_*

From d26108bf3ab971b05a7618f2f1c89e7ba76e4442 Mon Sep 17 00:00:00 2001
From: Sebastian Riedel <git@basxto.de>
Date: Fri, 4 Feb 2022 20:11:17 +0100
Subject: [PATCH 07/10] Invert file existence checks

---
 game/makefile | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/game/makefile b/game/makefile
index 2fd6471..50a3f9d 100644
--- a/game/makefile
+++ b/game/makefile
@@ -49,7 +49,7 @@ bin/$(ROM).gb: obj/game.ihx | bin/
 	$(MKROM) -Z -yn BUBBLEFACT -yk DH -yt 0x1B -ya 1 -yS -yp0x014C=1 $< $@
 	cp obj/game.sym bin/$(ROM).sym
 	cp obj/game.noi bin/$(ROM).noi
-	test -e obj/game.cdb && cp obj/game.cdb bin/$(ROM).cdb
+	test \! -s obj/game.cdb || cp obj/game.cdb bin/$(ROM).cdb
 
 obj/game.ihx: $(OBJFILES) | obj/
 	$(CC) $(LDFLAGS) $^ -o $@
@@ -67,11 +67,11 @@ spaceleft: build
 	$(ROMUSE) bin/$(ROM).noi -g -E
 
 statistics: build
-	test -e bin/$(ROM).cdb && $(ROMUSE) bin/$(ROM).cdb -g
+	test \! -s bin/$(ROM).cdb || $(ROMUSE) bin/$(ROM).cdb -g
 	$(ROMUSE) bin/$(ROM).noi -G -E -sH -a
 
 run: build
-	$(EMU) $(ROM)
+	$(EMU) bin/$(ROM).gb
 
 clean:
 	$(RM) -rf src/data_*

From 534e93c02a797c489c5376789ed3d25f123da137 Mon Sep 17 00:00:00 2001
From: Sebastian Riedel <git@basxto.de>
Date: Fri, 4 Feb 2022 20:46:05 +0100
Subject: [PATCH 08/10] Remove unnecessary old calling conventions

---
 game/src/gb.c      | 10 +++++-----
 game/src/gb.h      | 10 +++++-----
 game/src/memory.c  |  2 +-
 game/src/memory.h  |  2 +-
 game/src/sprites.c |  2 +-
 game/src/sprites.h |  2 +-
 6 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/game/src/gb.c b/game/src/gb.c
index a887eaa..f99113a 100644
--- a/game/src/gb.c
+++ b/game/src/gb.c
@@ -16,7 +16,7 @@ GBJoypadState gbJoypadReleasedSinceLastUpdate;
 // ===
 // Public API
 // ===
-void gbLCDDisable() __sdcccall(0) {
+void gbLCDDisable() {
     __asm
     
     push af
@@ -36,28 +36,28 @@ void gbLCDDisable() __sdcccall(0) {
     __endasm;
 }
 
-void gbLCDEnable() __sdcccall(0) {
+void gbLCDEnable() {
     __asm
     ld hl, #0xff40
     set #7, (hl)
     __endasm;
 }
 
-void gbSpritesDisable() __sdcccall(0) {
+void gbSpritesDisable() {
     __asm
     ld hl, #0xff40
     res #1, (hl)
     __endasm;
 }
 
-void gbSpritesEnable() __sdcccall(0) {
+void gbSpritesEnable() {
     __asm
     ld hl, #0xff40
     set #1, (hl)
     __endasm;
 }
 
-void gbJoypadStateUpdate() __sdcccall(0) {
+void gbJoypadStateUpdate() {
     GBUInt8 lastValue;
     
     lastValue = gbJoypadState;
diff --git a/game/src/gb.h b/game/src/gb.h
index fe62261..fc8c216 100644
--- a/game/src/gb.h
+++ b/game/src/gb.h
@@ -79,13 +79,13 @@ extern GBJoypadState gbJoypadState;
 extern GBJoypadState gbJoypadPressedSinceLastUpdate;
 extern GBJoypadState gbJoypadReleasedSinceLastUpdate;
 
-void gbLCDDisable() __sdcccall(0);
-void gbLCDEnable() __sdcccall(0);
+void gbLCDDisable();
+void gbLCDEnable();
 
-void gbSpritesDisable() __sdcccall(0);
-void gbSpritesEnable() __sdcccall(0);
+void gbSpritesDisable();
+void gbSpritesEnable();
 
-void gbJoypadStateUpdate() __sdcccall(0);
+void gbJoypadStateUpdate();
 
 void gbLogUInt8(GBUInt8 value) __sdcccall(0);
 void gbLogUInt16(GBUInt16 value) __sdcccall(0);
diff --git a/game/src/memory.c b/game/src/memory.c
index 76d6290..d8db993 100644
--- a/game/src/memory.c
+++ b/game/src/memory.c
@@ -4,7 +4,7 @@ volatile const void * memoryCopySourceAddress;
 volatile void * memoryCopyDestinationAddress;
 volatile GBUInt8 memoryCopyLength;
 
-void memoryCopy() __sdcccall(0) {
+void memoryCopy() {
     __asm
     
     push af
diff --git a/game/src/memory.h b/game/src/memory.h
index 25b4d67..db800fc 100644
--- a/game/src/memory.h
+++ b/game/src/memory.h
@@ -7,6 +7,6 @@ extern volatile const void * memoryCopySourceAddress;
 extern volatile void * memoryCopyDestinationAddress;
 extern volatile GBUInt8 memoryCopyLength;
 
-void memoryCopy() __sdcccall(0);
+void memoryCopy();
 
 #endif
diff --git a/game/src/sprites.c b/game/src/sprites.c
index a8b0bd8..d4c446c 100644
--- a/game/src/sprites.c
+++ b/game/src/sprites.c
@@ -35,7 +35,7 @@ void spritesInit() {
     tempAnimationPhase = 0;
 }
 
-void spritesWriteToOAM() __sdcccall(0) {
+void spritesWriteToOAM() {
     __asm
     call #0xFF80
     __endasm;
diff --git a/game/src/sprites.h b/game/src/sprites.h
index 6cac954..149ba12 100644
--- a/game/src/sprites.h
+++ b/game/src/sprites.h
@@ -38,7 +38,7 @@ extern volatile const SpriteFrameAttributes * spritesWriteAttributes;
 #define spritesAttributesMake(priority, flipX, flipY, paletteNumber) (((priority) << 7) | ((flipX) << 5) | ((flipY) << 6) | ((paletteNumber) << 4))
 
 void spritesInit();
-void spritesWriteToOAM() __sdcccall(0);
+void spritesWriteToOAM();
 void spritesWrite2x2();
 void spritesWrite1x1();
 

From d7de030a8ce36016840fb8381d2c728bd5043533 Mon Sep 17 00:00:00 2001
From: Sebastian Riedel <git@basxto.de>
Date: Fri, 4 Feb 2022 22:40:29 +0100
Subject: [PATCH 09/10] Rewrite asm for new calling convention

---
 game/src/gb.c     | 24 +++++---------------
 game/src/gb.h     |  4 ++--
 game/src/map.c    | 56 ++++++++++++++---------------------------------
 game/src/memory.c | 39 ++++++++++++---------------------
 game/src/memory.h |  4 +---
 5 files changed, 38 insertions(+), 89 deletions(-)

diff --git a/game/src/gb.c b/game/src/gb.c
index f99113a..1414322 100644
--- a/game/src/gb.c
+++ b/game/src/gb.c
@@ -109,44 +109,30 @@ void gbJoypadStateUpdate() {
     gbJoypadReleasedSinceLastUpdate = (gbJoypadState ^ lastValue) & lastValue;
 }
 
-void gbLogUInt8(GBUInt8 value) __sdcccall(0) {
+// 8bit in a
+void gbLogUInt8(GBUInt8 value) {
     (void)(value); // Suppresses unused variable warning
     
     __asm
-    push af
-    push hl
-    ldhl sp, #3
-    ld a, (hl)
     ld d, d
     jr .gbLogUInt8End
     .dw 0x6464
     .dw 0x0000
     .strz "0x%a%"
 .gbLogUInt8End:
-    pop hl
-    pop af
     __endasm;
 }
 
-void gbLogUInt16(GBUInt16 value) __sdcccall(0) {
+// 16bit in de
+void gbLogUInt16(GBUInt16 value) {
     (void)(value); // Suppresses unused variable warning
     
     __asm
-    push af
-    push bc
-    push hl
-    ldhl sp, #8
-    ld a, (hl+)
-    ld c, a
-    ld b, (hl)
     ld d, d
     jr .gbLogUInt16End
     .dw 0x6464
     .dw 0x0000
-    .strz "0x%bc%"
+    .strz "0x%de%"
 .gbLogUInt16End:
-    pop hl
-    pop bc
-    pop af
     __endasm;
 }
diff --git a/game/src/gb.h b/game/src/gb.h
index fc8c216..39cb73a 100644
--- a/game/src/gb.h
+++ b/game/src/gb.h
@@ -87,7 +87,7 @@ void gbSpritesEnable();
 
 void gbJoypadStateUpdate();
 
-void gbLogUInt8(GBUInt8 value) __sdcccall(0);
-void gbLogUInt16(GBUInt16 value) __sdcccall(0);
+void gbLogUInt8(GBUInt8 value);
+void gbLogUInt16(GBUInt16 value);
 
 #endif /* gb_h */
diff --git a/game/src/map.c b/game/src/map.c
index e901d71..62b89e7 100644
--- a/game/src/map.c
+++ b/game/src/map.c
@@ -225,13 +225,9 @@ void mapUpdateGraphics() {
         _needsToRedrawHighScore = false;
         
         memoryCopyLength = 4;
-        memoryCopyDestinationAddress = gbTileMap0;
-        memoryCopySourceAddress = _highScoreMap[0];
-        memoryCopy();
-        
-        memoryCopyDestinationAddress = gbTileMap0 + 32;
-        memoryCopySourceAddress = _highScoreMap[1];
-        memoryCopy();
+        memoryCopy(gbTileMap0, _highScoreMap[0]);
+
+        memoryCopy(gbTileMap0 + 32, _highScoreMap[1]);
         
         return;
     }
@@ -240,13 +236,9 @@ void mapUpdateGraphics() {
         _needsToRedrawScore = false;
         
         memoryCopyLength = 4;
-        memoryCopyDestinationAddress = gbTileMap0 + 16;
-        memoryCopySourceAddress = _scoreMap[0];
-        memoryCopy();
-        
-        memoryCopyDestinationAddress = gbTileMap0 + 48;
-        memoryCopySourceAddress = _scoreMap[1];
-        memoryCopy();
+        memoryCopy(gbTileMap0 + 16, _scoreMap[0]);
+
+        memoryCopy(gbTileMap0 + 48, _scoreMap[1]);
         
         return;
     }
@@ -303,13 +295,9 @@ void mapUpdateGraphics() {
         if(_mapAnimationTickTime & 2) {
             // Top Left
             memoryCopyLength = 8;
-            memoryCopyDestinationAddress = gbTileMap0 + 67;
-            memoryCopySourceAddress = tileAnimations1[_mapAnimationCycle];
-            memoryCopy();
-            
-            memoryCopyDestinationAddress = gbTileMap0 + 99;
-            memoryCopySourceAddress = tileAnimations2[_mapAnimationCycle];
-            memoryCopy();
+            memoryCopy(gbTileMap0 + 67, tileAnimations1[_mapAnimationCycle]);
+
+            memoryCopy(gbTileMap0 + 99, tileAnimations2[_mapAnimationCycle]);
             
             if(bubblesIsTopInDanger()) {
                 if((_mapAnimationCycle & 1) == 0) {
@@ -328,35 +316,23 @@ void mapUpdateGraphics() {
         } else {
             // Top Right
             memoryCopyLength = 6;
-            memoryCopyDestinationAddress = gbTileMap0 + 75;
-            memoryCopySourceAddress = tileAnimations1[_mapAnimationCycle] + 8;
-            memoryCopy();
-            
-            memoryCopyDestinationAddress = gbTileMap0 + 107;
-            memoryCopySourceAddress = tileAnimations2[_mapAnimationCycle] + 8;
-            memoryCopy();
+            memoryCopy(gbTileMap0 + 75, tileAnimations1[_mapAnimationCycle] + 8);
+
+            memoryCopy(gbTileMap0 + 107, tileAnimations2[_mapAnimationCycle] + 8);
         }
     } else {
         if(_mapAnimationTickTime & 2) {
             // Bottom Left
             memoryCopyLength = 8;
-            memoryCopyDestinationAddress = gbTileMap0 + 451;
-            memoryCopySourceAddress = tileAnimations3[_mapAnimationCycle];
-            memoryCopy();
+            memoryCopy(gbTileMap0 + 451, tileAnimations3[_mapAnimationCycle]);
             
-            memoryCopyDestinationAddress = gbTileMap0 + 483;
-            memoryCopySourceAddress = tileAnimations4[_mapAnimationCycle];
-            memoryCopy();
+            memoryCopy(gbTileMap0 + 483, tileAnimations4[_mapAnimationCycle]);
         } else {
             // Bottom Right
             memoryCopyLength = 6;
-            memoryCopyDestinationAddress = gbTileMap0 + 459;
-            memoryCopySourceAddress = tileAnimations3[_mapAnimationCycle] + 8;
-            memoryCopy();
+            memoryCopy(gbTileMap0 + 459, tileAnimations3[_mapAnimationCycle] + 8);
             
-            memoryCopyDestinationAddress = gbTileMap0 + 491;
-            memoryCopySourceAddress = tileAnimations4[_mapAnimationCycle] + 8;
-            memoryCopy();
+            memoryCopy(gbTileMap0 + 491, tileAnimations4[_mapAnimationCycle] + 8);
             
             if(bubblesIsBottomInDanger()) {
                 if((_mapAnimationCycle & 1) == 0) {
diff --git a/game/src/memory.c b/game/src/memory.c
index d8db993..cb4b119 100644
--- a/game/src/memory.c
+++ b/game/src/memory.c
@@ -1,45 +1,34 @@
 #include "memory.h"
 
-volatile const void * memoryCopySourceAddress;
-volatile void * memoryCopyDestinationAddress;
 volatile GBUInt8 memoryCopyLength;
 
-void memoryCopy() {
+void memoryCopy(void * dest, const void * src) {
+    // Suppresses unused variable warning
+    (void)(dest); // in de
+    (void)(src); // in bc
     __asm
-    
+
     push af
-    push bc
-    push de
-    
     ld hl, #_memoryCopyLength
-    ld c, (hl)
-    
-    ld hl, #_memoryCopyDestinationAddress
-    ld e, (hl)
-    inc hl
-    ld d, (hl)
-    
-    ld hl, #_memoryCopySourceAddress
     ld a, (hl)
-    inc hl
-    ld h, (hl)
-    ld l, a
-    
-.loop:
-    ld a, c
+
+    ld h, b
+    ld l, c
+
+    ld c, a
+
     or a
     jr z, .endLoop
+.loop:
     
     ld a, (hl+)
     ld (de), a
     inc de
+
     dec c
-    
-    jr .loop
+    jr nz, .loop
     
 .endLoop:
-    pop de
-    pop bc
     pop af
     
     __endasm;
diff --git a/game/src/memory.h b/game/src/memory.h
index db800fc..94cddfb 100644
--- a/game/src/memory.h
+++ b/game/src/memory.h
@@ -3,10 +3,8 @@
 
 #include "gb.h"
 
-extern volatile const void * memoryCopySourceAddress;
-extern volatile void * memoryCopyDestinationAddress;
 extern volatile GBUInt8 memoryCopyLength;
 
-void memoryCopy();
+void memoryCopy(void * dest, const void * src);
 
 #endif

From 819aa441aad1120ea0b08d3f9d8757e421ee8534 Mon Sep 17 00:00:00 2001
From: Sebastian Riedel <git@basxto.de>
Date: Fri, 4 Feb 2022 23:45:56 +0100
Subject: [PATCH 10/10] Optimize some asm

---
 game/src/crt0.s | 10 ++++------
 game/src/gb.c   | 33 ++++++++++++++++++++++-----------
 2 files changed, 26 insertions(+), 17 deletions(-)

diff --git a/game/src/crt0.s b/game/src/crt0.s
index f77c4af..f8ac85c 100644
--- a/game/src/crt0.s
+++ b/game/src/crt0.s
@@ -61,24 +61,22 @@
     ld sp, #0xE000
     
     ; initialize gamepad to 0
-    ld a, #0
+    xor a
     ld (_gbJoypadState), a
     
     ; install dma handler
     ld c, #(.endOAMDMA - .oamDMA)
     ld de, #0xFF80
     ld hl, #.oamDMA
+
+    ; c is never 0
 .installOAMDMALoop:
-    ld a, c
-    or a
-    jr z, .endInstallOAMDMALoop
-    
     ld a, (hl+)
     ld (de), a
     inc de
     
     dec c
-    jr .installOAMDMALoop
+    jr nz, .installOAMDMALoop
 .endInstallOAMDMALoop:
     
     call _main
diff --git a/game/src/gb.c b/game/src/gb.c
index 1414322..be7dac8 100644
--- a/game/src/gb.c
+++ b/game/src/gb.c
@@ -23,7 +23,7 @@ void gbLCDDisable() {
     
     ; busy wait for vblank
 .lcdDisableLoop:
-    ld a, (#0xff44)
+    ldh a, (#0xff44)
     cp a, #144
     jr nz, .lcdDisableLoop
     
@@ -69,29 +69,40 @@ void gbJoypadStateUpdate() {
     
     push af
     push bc
+    ld c, #0
     
     ; Read first part of joypad state
     ld a, #0x20
-    ld (#0xff00), a
+    ldh (c), a
     
     ; Read several times to burn cycles waiting for register to update
-    ld a, (#0xff00)
-    ld a, (#0xff00)
+    ; `ldh a, (c); ldh a, (c)` same amount of clocks
+    ; as `ld a, (#0xff00)` but one byte less
+    ldh a, (c)
+    ldh a, (c)
+    ldh a, (c)
+    ldh a, (c)
     cpl ; Invert so 1=on and 0=off
     and #0x0f ; Only want 4 least significant bits
     ld b, a ; Store in b
     
     ; Read second part of joypad state
     ld a, #0x10
-    ld (#0xff00), a
+    ldh (c), a
     
     ; Read several times to burn cycles waiting for register to update
-    ld a, (#0xff00)
-    ld a, (#0xff00)
-    ld a, (#0xff00)
-    ld a, (#0xff00)
-    ld a, (#0xff00)
-    ld a, (#0xff00)
+    ldh a, (c)
+    ldh a, (c)
+    ldh a, (c)
+    ldh a, (c)
+    ldh a, (c)
+    ldh a, (c)
+    ldh a, (c)
+    ldh a, (c)
+    ldh a, (c)
+    ldh a, (c)
+    ldh a, (c)
+    ldh a, (c)
     
     cpl ; invert
     and #0x0f ; only 4 least significant bits