Update mif

mwenge · Jul 16, 2024 · 698bb4d · 698bb4d
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diff --git a/src/mif.tex b/src/mif.tex
@@ -11,9 +11,25 @@ \chapter{Made in France}
 wondered if Jeff Minter had inadvertently invented a precursor to 'Snake', a text-based game that
 was once ubiqitous thanks to its inclusion on Nokia mobile phones in the 1990s, but it turns out that
 Snake dates back to at least 1976 when the concept first appeared in an arcade game called 'Blockade'.
+\begin{figure}[H]
+  {
+    \setlength{\tabcolsep}{3.0pt}
+    \setlength\cmidrulewidth{\heavyrulewidth} % Make cmidrule = 
+	\centering
+	\begin{subfigure}{0.5\textwidth}
+    \includegraphics[width=6cm]{src/mif/blockade.jpg}%
+	\end{subfigure}
+	\begin{subfigure}{0.5\textwidth}
+      \includegraphics[width=6cm]{src/mif/blockade2.jpg}%
+	\end{subfigure}
+  }
+
+\caption{'Blockade' from 1976, a two-player arcade game by Gremlin.}
+\end{figure}
 
 Perhaps the most noteworthy thing about 'Made in France' (MIF) is how many times Minter has made and remade it. His very
-first attempt at the format was one of his earliest games. 'Deflex' was coded in 1979 while he was in college and had access to a 
+first attempt at the format was one of his earliest games. 'Deflex' was coded in 1979 while he was in Queen Mary's Sixth Form college
+in Basingstoke and had access to a 
 Commodore PET. Viewed side by side it's obvious that one is a slightly more colorful
 remake of the other.
 
@@ -30,11 +46,12 @@ \chapter{Made in France}
 	\end{subfigure}
   }
 
-\caption{'Deflex' on the left, 'Made in France' on the right.}
+\caption{'Deflex' on the left, 'Made in France' on the right. The original Commodor PET version of 'Deflex' is lost, so in 2023 
+  \href{https://archive.org/details/deflex-remake}{\textcolor{blue}{Jeff Minter remade it!}}}
 \end{figure}
 
-MIF meanwhile was coded while on a ski holiday in France during the making of Iridis Alpha. Minter lugged his development kit on
-holiday to the Alps and continued work on Iridis Alpha between time on the slopes and in a couple of evenings remade Deflex into
+`Made in France' (or MIF for short) was coded while on a winter holiday in France during the making of Iridis Alpha. Minter lugged his development kit to
+a ski resort in the Alps and continued work between time on the slopes. Over a couple of spare evenings he remade Deflex into
 MIF. He shared this version on Compunet prior to the release of Iridis Alpha and the version that features in the game is unchanged
 from that original version.
 
@@ -47,10 +64,44 @@ \chapter{Made in France}
     \setlength\cmidrulewidth{\heavyrulewidth} % Make cmidrule = 
 	\centering
 	\begin{subfigure}{0.5\textwidth}
-      \includegraphics[width=6cm]{src/mif/pet_nm.jpg}%
+      \frame{\includegraphics[width=6cm]{src/mif/deflex.png}}
+	\end{subfigure}
+	\begin{subfigure}{0.5\textwidth}
+      \frame{\includegraphics[width=6cm]{src/mif/DeflexV_VIC20.png}}
+	\end{subfigure}
+	\begin{subfigure}{0.5\textwidth}
+  \vspace{0.3cm}
+      \frame{\includegraphics[width=6cm]{src/mif/SuperDeflex_ZXSpectrum.png}}
+	\end{subfigure}
+	\begin{subfigure}{0.5\textwidth}
+  \vspace{0.3cm}
+      \frame{\includegraphics[width=6cm]{src/mif/TurboFlexAtari.png}}
+	\end{subfigure}
+	\begin{subfigure}{0.5\textwidth}
+  \vspace{0.3cm}
+      \frame{\includegraphics[width=6cm]{src/mif/Deflex_PocketPC.png}}
 	\end{subfigure}
 	\begin{subfigure}{0.5\textwidth}
-      \includegraphics[width=6cm]{src/mif/c64_nm.jpg}%
+  \vspace{0.3cm}
+      \frame{\includegraphics[width=6cm]{src/mif/Deflex_IOS.png}}
+	\end{subfigure}
+  }
+\caption{Deflex through the ages. }
+\end{figure}
+\clearpage
+
+The most striking thing to the modern player is the controls. You place paddles (or deflectors) by using the 'N' and 'M' keys. At first
+this seems inexplicable: why not use arrow keys instead? The answer lies in the layout of the C64 and Commodore Pet keyboards: 
+\begin{figure}[H]
+  {
+    \setlength{\tabcolsep}{3.0pt}
+    \setlength\cmidrulewidth{\heavyrulewidth} % Make cmidrule = 
+	\centering
+	\begin{subfigure}{0.5\textwidth}
+    \frame{\includegraphics[width=6cm]{src/mif/pet_nm.jpg}}
+	\end{subfigure}
+	\begin{subfigure}{0.5\textwidth}
+    \frame{\includegraphics[width=6cm]{src/mif/c64_nm.jpg}}
 	\end{subfigure}
   }
 \caption{ The controls seem unintuitive to a player using a C64 emulator. Why use 'M' and 'N' for placing paddles? The answer lies in the PET
@@ -61,8 +112,8 @@ \chapter{Made in France}
 \subsubsection{Main Loop}
 The code for MIF comes in at a relatively light 900 or so lines of 6502
 assembler. The main loop of the game is primarily concerned with detecting key
-presses to enter into the DNA mini-game, see
-\hyperref[sec:dna]{\textcolor{blue}{A Pause Mode for Your Pause Mode}} or exit
+presses to enter into the DNA mini-game (see
+\hyperref[sec:dna]{\textcolor{blue}{A Pause Mode for Your Pause Mode}}) or exit
 back to Iridis Alpha itself.
 
 \begin{lstlisting}[escapechar=\%]
@@ -139,6 +190,191 @@ \subsubsection{Main Loop}
     JMP $EA31
 \end{lstlisting}
 
-Minter has written up a bit more on the \href{https://web.archive.org/web/20230811235533/https://stinkygoat.livejournal.com/211183.html}{history of Deflex} and
-its various incarnations throughout the years.
+\subsubsection{A Target Explodes}
+One point of interest in this mini-game is the explosion when you finally overcome the
+frustrating controls and manage to strike the target with your snake.
+\begin{figure}[H]
+    \centering
+    \foreach \l in {1, ..., 6}
+    {
+      \begin{subfigure}{0.3\textwidth}
+      \includegraphics[width=3cm]{mif/explosion/\l-crop.png}%
+      \end{subfigure}
+    }%
+\caption{Stages in the target's explosion}
+\end{figure}
+
+If we carefully examine the sequence of the explosion above it is possible to discern what
+is going on. At each step we paint eight red squares. In the first step, these eight squares will
+enclose our target giving us a solid block. 
+\begin{figure}[H]
+    \centering
+      \frame{\includegraphics[width=3cm]{mif/explosion/1-crop.png}}%
+\caption{Step One}
+\end{figure}
+
+In the following step, we paint eight red squares again but this time we separate each with a single space.
+We also paint eight squares again like we did in the first step, but this time in the colour brown.
+\begin{figure}[H]
+    \centering
+      \frame{\includegraphics[width=3cm]{mif/explosion/2-crop.png}}%
+\caption{Step Two}
+\end{figure}
+
+In the third step, we paint eight red squares again but this time we separate each with two spaces.
+We also paint eight squares separated by a single space, but this time in the color brown.
+Finally we paint eight sqaures separated by no spaces and this time in the colour yellow.
+\begin{figure}[H]
+    \centering
+      \frame{\includegraphics[width=3cm]{mif/explosion/3-crop.png}}%
+\caption{Step Three}
+\end{figure}
+
+Are you beginning to get the idea? We do this until we have used up all 8 colours and we keep exploding
+until we have reached a limit of 48 spaces between squares. 
+
+Here is the routine that runs every time the
+interrupt is called and there's an explosion in progress. It maintains the current outer limit of the 
+explosion in \icode{previousSpacesBetweenSquares} and works inwards each time it is called, painting the
+layers of the explosion in ever-decreasing circles:
+
+\begin{lstlisting}[escapechar=\%, caption=The routine responsible for animating a frame of the explosion\, it will
+keep getting called until it sets \icode{targetIsExploding} to \icode{\$00}.]
+DoAnExplosionFrame
+		    LDA #$A0
+        STA mifCurrentChar
+        LDA previousSpacesBetweenSquares
+        STA spacesBetweenSquares
+        LDA #$00
+        STA currentColor
+
+PopulateAStageInTheExplosionLoop   
+        JSR PopulateAStageInTheExplosion
+        INC currentColor
+        LDA currentColor
+        CMP #$08 ; Until we have 8 distinct colors
+        BEQ CheckIfExplosionFinished
+        DEC spacesBetweenSquares
+        BNE PopulateAStageInTheExplosionLoop
+
+CheckIfExplosionFinished   
+        INC previousSpacesBetweenSquares
+        LDA previousSpacesBetweenSquares
+        CMP #48 ; Until we have 48 spaces between squares
+        BEQ ExplosionFinished
+        RTS 
+
+ExplosionFinished   
+        LDA #$00
+        STA targetIsExploding
+        RTS 
+
+\end{lstlisting}
+
+The actual 'painting of squares to the screen' is performed by the \icode{PopulateAStageIn\-TheExplosion} routine
+given below. Notice that this is what is called an 'unrolled loop'. That is, it would be possible to write this
+as a loop of some sort but it is in fact simpler and more performant (at the expense of being more verbose) to just
+write out the painting of all eight squares individually rather than refactor them into an interation:
+
+\begin{lstlisting}[escapechar=\%, caption=The routine responsible for animating a frame of the explosion\, it will
+keep getting called until it sets \icode{targetIsExploding} to \icode{\$00}.]
+PopulateAStageInTheExplosion   
+        LDX mifTargetCurrentColor
+        LDA mifSnakeColorArray,X
+        STA mifCurrentCharColor
+
+        LDA mifRandomXPos
+        SEC 
+        SBC spacesBetweenSquares
+        STA mifCurrentXPos
+        LDA mifRandomYPos
+        SEC 
+        SBC spacesBetweenSquares
+        STA mifCurrentYPos
+        JSR DrawCharacterIfItsStillOnScreen
+
+        LDA mifCurrentXPos
+        CLC 
+        ADC spacesBetweenSquares
+        STA mifCurrentXPos
+        JSR DrawCharacterIfItsStillOnScreen
+
+        LDA mifCurrentXPos
+        CLC 
+        ADC spacesBetweenSquares
+        STA mifCurrentXPos
+        JSR DrawCharacterIfItsStillOnScreen
+
+        LDA mifCurrentYPos
+        CLC 
+        ADC spacesBetweenSquares
+        STA mifCurrentYPos
+        JSR DrawCharacterIfItsStillOnScreen
+
+        LDA mifCurrentYPos
+        CLC 
+        ADC spacesBetweenSquares
+        STA mifCurrentYPos
+        JSR DrawCharacterIfItsStillOnScreen
+
+        LDA mifCurrentXPos
+        SEC 
+        SBC spacesBetweenSquares
+        STA mifCurrentXPos
+        JSR DrawCharacterIfItsStillOnScreen
+
+        LDA mifCurrentXPos
+        SEC 
+        SBC spacesBetweenSquares
+        STA mifCurrentXPos
+        JSR DrawCharacterIfItsStillOnScreen
+
+        LDA mifCurrentYPos
+        SEC 
+        SBC spacesBetweenSquares
+        STA mifCurrentYPos
+
+DrawCharacterIfItsStillOnScreen   
+        LDA mifCurrentXPos
+        BMI CharacterIsOffScreen
+        CMP #$27
+        BMI CheckYPosOfCurrentChar
+CharacterIsOffScreen   
+        RTS 
+
+CheckYPosOfCurrentChar   
+        LDA mifCurrentYPos
+        BMI CharacterIsOffScreen
+        CMP #$16
+        BMI CharacterIsOnScreen
+        RTS 
+
+CharacterIsOnScreen   
+        JMP DrawCurrentCharAtCurrentPos
+
+
+\end{lstlisting}
+
+Notice that painting the eighth square is achieved by simply falling through to \icode{DrawCharacterIf\-ItsStillOnScreen},
+whereas for each of the previous seven squares this subroutine is called and returned from.
+
+I also quite like the simple logic at the end of the routine to ensure we don't bother trying to paint characters that are
+not on the screen. As a whole, this routine this code leverages nicely the 'return early' pattern possible in assembly programming
+where we bail out early if a condition is not met and otherwise let the code proceed to execute to the end and do what needs
+to be done \textit{only if it needs to be done}.
+
+\begin{figure}[H]
+    \centering
+    \foreach \l in {1, ..., 15}
+    {
+      \begin{subfigure}{0.3\textwidth}
+        \vspace{0.2cm}
+      \includegraphics[width=3cm]{mif/explosion/\l.png}%
+      \end{subfigure}
+    }%
+\caption{A full explosion sequence.}
+\end{figure}
+
+%Minter has written up a bit more on the \href{https://web.archive.org/web/20230811235533/https://stinkygoat.livejournal.com/211183.html}{history of Deflex} and
+%its various incarnations throughout the years.
 
diff --git a/src/mif/DeflexV_VIC20.png b/src/mif/DeflexV_VIC20.png
diff --git a/src/mif/Deflex_IOS.png b/src/mif/Deflex_IOS.png
diff --git a/src/mif/Deflex_PocketPC.png b/src/mif/Deflex_PocketPC.png
diff --git a/src/mif/SuperDeflex_ZXSpectrum.png b/src/mif/SuperDeflex_ZXSpectrum.png
diff --git a/src/mif/TurboFlexAtari.png b/src/mif/TurboFlexAtari.png
diff --git a/src/mif/blockade.jpg b/src/mif/blockade.jpg
diff --git a/src/mif/blockade2.jpg b/src/mif/blockade2.jpg
diff --git a/src/mif/blockage2.jpg b/src/mif/blockage2.jpg
diff --git a/src/mif/explosion/1-crop.png b/src/mif/explosion/1-crop.png
diff --git a/src/mif/explosion/1.png b/src/mif/explosion/1.png
diff --git a/src/mif/explosion/10.png b/src/mif/explosion/10.png
diff --git a/src/mif/explosion/11.png b/src/mif/explosion/11.png
diff --git a/src/mif/explosion/12.png b/src/mif/explosion/12.png
diff --git a/src/mif/explosion/13.png b/src/mif/explosion/13.png
diff --git a/src/mif/explosion/14.png b/src/mif/explosion/14.png
diff --git a/src/mif/explosion/15.png b/src/mif/explosion/15.png
diff --git a/src/mif/explosion/16.png b/src/mif/explosion/16.png
diff --git a/src/mif/explosion/2-crop.png b/src/mif/explosion/2-crop.png
diff --git a/src/mif/explosion/2.png b/src/mif/explosion/2.png
diff --git a/src/mif/explosion/3-crop.png b/src/mif/explosion/3-crop.png
diff --git a/src/mif/explosion/3.png b/src/mif/explosion/3.png
diff --git a/src/mif/explosion/4-crop.png b/src/mif/explosion/4-crop.png
diff --git a/src/mif/explosion/4.png b/src/mif/explosion/4.png
diff --git a/src/mif/explosion/5-crop.png b/src/mif/explosion/5-crop.png
diff --git a/src/mif/explosion/5.png b/src/mif/explosion/5.png
diff --git a/src/mif/explosion/6-crop.png b/src/mif/explosion/6-crop.png
diff --git a/src/mif/explosion/6.png b/src/mif/explosion/6.png
diff --git a/src/mif/explosion/7.png b/src/mif/explosion/7.png
diff --git a/src/mif/explosion/8.png b/src/mif/explosion/8.png
diff --git a/src/mif/explosion/9.png b/src/mif/explosion/9.png
diff --git a/src/titlescreen.tex b/src/titlescreen.tex
@@ -1045,7 +1045,7 @@ \section{Title Text}
     \foreach \l in {59, 61, ..., 70}
     {
       \begin{subfigure}{0.3\textwidth}
-      \includegraphics[width=4cm]{titlescreen/title\l.png}%
+        \frame{\includegraphics[width=4cm]{titlescreen/title\l.png}}%
       \end{subfigure}
     }%
 \caption{The title text is finally revealed}