Expand the README.md file

Most of the things from the CHANGELOG.md file didn't belong there, and
so I've made them a proper section on the README.md file.

Signed-off-by: Miquel Sabaté Solà <mssola@mssola.com>

2 files changed, 102 insertions, 31 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f0fbde8..2b0aacf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,30 +1,5 @@
 # 1.0 (Under development)
 
-The game tries to be close to the original ZX Spectrum version, while being
-adapted to the reality of the NES/Famicom. This means:
+Initial implementation of the full game.
 
-- The player is presented with a **title screen** which is a merge between the
-  "Loading" and the title screens from the ZX Spectrum. On the NES/Famicom the
-  concept of "loading" is quite foreign to players (unless your are on the
-  [Famicom Disk System](https://en.wikipedia.org/wiki/Famicom_Disk_System), of
-  course), but at the same time I wanted to re-use at least some of its elements
-  on the otherwise quite blank title screen from the original. Hence, both
-  screens have been merged into something that feels more like it belongs to the
-  NES/Famicom library.
-- **Colors** are slightly different because of palette differences between the
-  NES/Famicom and the ZX Spectrum. That being said, some colors have been
-  rearranged on purpose, like the red on the jetpac's fire or the general change
-  on the title screen (because it's a new thing altogether).
-- The **controls** of the player should be quite close to the original, even if
-  physics might be a bit different here and there. Overall, it shouldn't be too
-  distracting and I'm fine with them being slightly different to the original.
-- **Shooting** is something that is completely different to the original, as the
-  NES/Famicom presents a sprite limit per scanline which is quite daunting for a
-  shooter. I also envisioned doing nasty things on background tiles, but that is
-  hard to do and probably not worth it. In the end: different machine, different
-  rules. Hence, bullets are handled in a similar way as other games for the
-  NES/Famicom, even if it's not particularly close to the original.
-- As an homage to Donkey Kong 64, you can **collect a coin** after completing 16
-  stages. This coin features a chameleon as a reference to SUSE, since I
-  originally bootstrapped this project during [Hackweek
-  23](https://hackweek.opensuse.org/projects/port-the-jetpac-game-to-the-nes).
+TODO: sccount, commits, and other statistics.
diff --git a/README.md b/README.md
index d83ba48..a1e7749 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ page](https://github.com/mssola/jetpac.nes/releases). Read the
 [CONTRIBUTING.md](./CONTRIBUTING.md) file if you want to make any changes,
 report an issue or make a suggestion.
 
-## The game
+# The game
 
 The game is a shooter in which you have to re-assemble your ship's parts and
 fill it with fuel, all while killing enemies that keep popping up. In the game
@@ -20,10 +20,106 @@ the controls are as follows:
 | <kbd>Arrow Down</kbd>                          | Hover                  |
 | <kbd>B</kbd>                                   | Shoot                  |
 
-Other than that, read the [CHANGELOG.md](./CHANGELOG.md) file for details on
-what's different from the original and what to expect from this port.
+# Changes from the original
 
-## License
+This port does not even attempt to be an exact replica of the original
+game. This is in line to what most ports felt during those times. That is, for a
+given game that was ported to multiple systems, you could always tell
+differences, and not just aesthetic ones.
+
+Being more specific, this port follows the original version with some
+adjustments in order to make it a reality on the NES/Famicom, but I have not
+been shy either on making some changes from my own taste. Read more on these
+changes below.
+
+## Merging the "loading" and the "title" screens
+
+The player is presented with a title screen which is a merge between the
+"Loading" and the title screens from the ZX Spectrum. On the NES/Famicom the
+concept of "loading" is quite foreign to players (unless your are on the
+[Famicom Disk System](https://en.wikipedia.org/wiki/Famicom_Disk_System), of
+course), but at the same time I wanted to re-use at least some of its elements
+on the otherwise quite blank title screen from the original. Hence, both screens
+have been merged into something that feels more like it belongs to the
+NES/Famicom library.
+
+## Colors
+
+One of the cool aspects from the original is how colorful things are. I have
+tried to keep things the same way, but there are some considerations to be made.
+
+First of all, colors are slightly different because of palette differences
+between the NES/Famicom and the ZX Spectrum. Thus, don't expect the same
+gradience of colors. More than that, some colors have been rearranged on
+purpose, like the red on the jetpac's fire, just because I felt it was nicer and
+it fit well with the overall coloring scheme.
+
+The colors from bullets are also quite hard to pin down from the
+original. Hence, I've done something that looks colorful and which is within the
+palettes for this game. Couple this with what I mention below on shooting, and
+you will quickly realize that shooting is a different experience than the
+original version. Hopefully this is not too distracting to players which were
+used at the original aesthetics.
+
+Finally, whenever the player fills the shuttle with fuel tanks, the original
+version displayed a small step of purple being filled in the shuttle. In the
+NES/Famicom world this is basically done via [PPU attribute
+tables](https://www.nesdev.org/wiki/PPU_attribute_tables), which cannot be that
+precise. Hence, instead of doing it by purely vertical steps, you will notice
+that the shuttle changes color in a slightly different way than in the
+original. Also, note that the shuttle won't start blinking when full, as I find
+it distracting.
+
+## Controls
+
+The controls of the player should be quite close to the original, even if
+physics might be a bit different here and there. Overall, it shouldn't be too
+distracting and I'm fine with them being slightly different to the original.
+
+## Shooting
+
+Shooting is something that is completely different to the original, as the
+NES/Famicom presents a sprite limit per scanline which is quite daunting for a
+shooter. I also envisioned doing nasty things on background tiles, but that is
+hard to do and probably not worth it. In the end: different machine, different
+rules. Hence, bullets are handled in a similar way as other games for the
+NES/Famicom, even if it's not particularly close to the original.
+
+## Scores
+
+The amount of points gained on each event is basically as in the original (note
+that some remakes re-arranged some of these things). But other than that, note
+that shuttle parts and fuel tanks are only accounted when you drop them, not
+when they are grabbed. This is different to the original game, but it made
+things more simple on the technical side, and I actually believe it makes more
+sense.
+
+## SUSE coin
+
+As an homage to Donkey Kong 64, you can collect a coin after completing 16
+stages. This coin features a chameleon as a reference to SUSE, since I
+originally bootstrapped this project during [Hackweek
+23](https://hackweek.opensuse.org/projects/port-the-jetpac-game-to-the-nes).
+
+# Technical thingies
+
+This game is designed for the [NROM](https://www.nesdev.org/wiki/NROM) cartridge
+board. Specifically, the 32K on PRG ROM capacity, and 8K on CHR ROM
+capacity. This is the most basic cartridge board available, and it was more than
+enough for this simple game. In fact, despite being completely careless on ROM
+space, I only ended up filling ~30% of ROM space for this basic configuration
+(check the exact numbers in the [CHANGELOG.md](./CHANGELOG.md) file).
+
+Moreover, this is a game that doesn't do any scrolling. Thus, I could've picked
+up any kind of mirroring for it, but here I'm using the horizontal one.
+
+Last but not least, the build system produces both an NTSC and a PAL version of
+the game. Coming from PAL territory myself, I've made an effort to make them
+feel more or less the same way. That is, the PAL version shouldn't feel slower
+in any way than the NTSC one. If that's not the case for you, [report an
+issue](https://github.com/mssola/jetpac.nes/issues).
+
+# License
 
 The original game was developed and published by Ashby Computers and Graphics
 Limited (trading as Ultimate Play the Game), and released for the ZX Spectrum