Simplify and improve INSTALL.md

1 files changed, 20 insertions, 34 deletions

diff --git a/INSTALL.md b/INSTALL.md
index 745f70007..030912d8e 100644
--- a/INSTALL.md
+++ b/INSTALL.md
@@ -1,51 +1,37 @@
-Run the following commands (first, see [this](#macos) if you are on **macOS** or [this](#old-windows) if you are on **old Windows**):
+## Prerequisites
 
-	git clone https://github.com/pret/pokefirered
-	git clone https://github.com/pikalaxalt/agbcc -b new_layout_with_libs
-
-	cd agbcc
-	make
-	make install prefix=../pokefirered
-
-	cd ../pokefirered
-
-To build **pokefirered.gba**:
-
-	make -j$(nproc)
+Until further notice, this repository requires a **baserom.gba** file, which must be [a legitimate copy of English Pokémon FireRed v1.0](https://datomatic.no-intro.org/?page=show_record&s=23&n=1616). See [this article](https://www.howtogeek.com/67241/htg-explains-what-are-md5-sha-1-hashes-and-how-do-i-check-them/) for help on how to verify the checksum.
 
-If you have only changed `.c` or `.s` files, you can turn off the dependency scanning temporarily. Changes to any other files will be ignored, and the build will either fail or not reflect those changes.
+----
 
-	make -j$(nproc) NODEP=1
-
-
-## macOS
+**Linux:** Proceed to [Installation](#installation).
 
-Run `xcode-select --install` in Terminal, then proceed by executing the commands.
+**macOS:** Get the [Xcode command-line tools](https://developer.apple.com/library/archive/technotes/tn2339/_index.html#//apple_ref/doc/uid/DTS40014588-CH1-DOWNLOADING_COMMAND_LINE_TOOLS_IS_NOT_AVAILABLE_IN_XCODE_FOR_MACOS_10_9__HOW_CAN_I_INSTALL_THEM_ON_MY_MACHINE_).
 
+**Windows 10 (1709+):** Get the [Windows Subsystem for Linux](https://docs.microsoft.com/windows/wsl/install-win10). For **Windows 10 (1607 & 1703)**, go [here](https://docs.microsoft.com/windows/wsl/install-legacy) instead.
 
-## Old Windows
+**Windows Vista, 7, 8, 8.1, and 10 (1507 & 1511):** Get [Cygwin](https://cygwin.com/install.html) and [include](https://cygwin.com/cygwin-ug-net/setup-net.html#setup-packages) the `make`, `git`, `gcc-core`, `gcc-g++`, `libpng-devel` packages.
 
-*For Windows 8.1 and earlier*
 
-Download and run the [Cygwin](https://www.cygwin.com/install.html) setup, leaving the default settings intact. At "Select Packages", set the view to "Full" and choose to install the following:
+## Installation
 
-- `make`
-- `git`
-- `gcc-core`
-- `gcc-g++`
-- `libpng-devel`
+To set up the repository:
 
-In the Cygwin command prompt, enter the commands.
+	git clone https://github.com/pret/pokefirered
+	git clone https://github.com/luckytyphlosion/agbcc -b new_layout_with_libs
 
-If the command for building pokefirered.gba does not work, run `nproc` and use that value instead of `$(nproc)` for `make`.
+	cd agbcc
+	make
+	make install prefix=../pokefirered
 
+	cd ../pokefirered
 
-## Windows 10
+To build **pokefirered.gba**:
 
-Install the [Windows Subsystem for Linux](https://docs.microsoft.com/windows/wsl/install-win10), and run the commands.
+	make -j$(nproc)
 
-## Important note for all users
+**Note:** If only `.c` or `.s` files were changed, turn off the dependency scanning temporarily. Changes to any other files will be ignored and the build will either fail or not reflect those changes.
 
-Until further notice, this repository is dependent on `baserom.gba`, which is a copy of Pokémon FireRed (U)(1.0) bearing the SHA1 sum `41cb23d8dccc8ebd7c649cd8fbb58eeace6e2fdc`.  If you attempt to build and get the following error or similar, it's because `baserom.gba` is missing.
+	make -j$(nproc) NODEP=1
 
-    No rule to make target 'build/firered/data/librfu_rodata.o', needed by 'pokefirered.elf'. Stop.
+**Note 2:** If the build command is not recognized on Linux, including the Linux environment used within Windows, run `nproc` and replace `$(nproc)` with the returned value (e.g.: `make -j4`). Because `nproc` is not available on macOS, the alternative is `sysctl -n hw.ncpu`.