Main.tex

\documentclass{article}

\usepackage[paperheight=10.5cm,paperwidth=10cm]{geometry}
\pagenumbering{gobble}

\usepackage{tikz}
\usepackage{ifthen}
\usepackage{animate}
\usepackage{media9}
\usepackage[absolute,overlay]{textpos}

\usepackage[pdfstartview=Fit]{hyperref}

\input{draw_snake.tex}

\pgfmathsetmacro\gameSize{8}

\pgfmathparse{\gameSize+1}\pgfmathsetmacro\boardSize{\pgfmathresult}

\textblockorigin{0.5cm}{1cm}
\setlength{\TPHorizModule}{1cm}
\setlength{\TPVertModule}{1cm}

\newcommand{\makeSnakeGame}{
\pdfpageattr{/AA <<
/O << /S/JavaScript /JS (
gameSize = 8;
gameSpeed = 300;
animations = [];
function set_segment(xy,val) {
    animations[xy[0]][xy[1]].frameNum = val;
}
segments = [[14, 15, -1, 16], [17, 13, 16, -1], [-1, 18, 14, 17], [18, -1, 15, 13]];
function init() {
    anim["intro"].frameNum = 1;
    anim["score"].frameNum = 4;
    while(animations.length) animations.pop();
    for(i = 0; i < gameSize; i++) {
        animations.push([]);
        for(j = 0; j < gameSize; j++)
            animations[i].push(anim["cell" + i + "x" + j]);
    }
    snake = [[0,0,-1], [1,0,4], [2,0,4], [3,0,4]];
    old_direction = 3;
    direction = 0;
    for(i = 0; i < gameSize; i++)
        for(j = 0; j < gameSize; j++)
            set_segment([i,j],0);
    set_segment(snake[0], 4);
    set_segment(snake[1], 13);
    set_segment(snake[2], 13);
    set_segment(snake[3], 8);
    add_food();
    alive = true;
}
function update_snake() {
    new_head = snake[snake.length - 1].slice(0);
    if(direction == 0) new_head[1] += 1;
    else if(direction == 1) new_head[0] -= 1;
    else if(direction == 2) new_head[1] -= 1;
    else if(direction == 3) new_head[0] += 1;
    die = Math.min(new_head[0], new_head[1]) < 0 || Math.max(new_head[0], new_head[1]) >= gameSize;
    for(i = 0; i < snake.length - 1; i++)
        die |= snake[i][0] == new_head[0] && snake[i][1] == new_head[1];
    if(die) {
        set_segment(snake[snake.length - 1], old_direction+9);
        return false;
    }
    grow = animations[new_head[0]][new_head[1]].frameNum == 19;
    new_head[2] = direction+1;
    snake.push(new_head);
    set_segment(new_head, direction+5);
    set_segment(snake[snake.length - 2], segments[direction][old_direction]);
    if(grow) {
        add_food();
        anim["score"].frameNum = snake.length;
    } else {
        set_segment(snake.shift(), 0);
        set_segment(snake[0], snake[1][2]);
    }
    old_direction = direction;
    return true;
}
function add_food() {
    outer:
    while(true) {
        x = Math.floor(gameSize*Math.random());
        y = Math.floor(gameSize*Math.random());
        for(i = 0; i < snake.length; i++)
            if(snake[i][0] == x && snake[i][1] == y)
                continue outer;
        set_segment([x, y], 19);
        return;
    }
}
function set_direction(dir) {
    if(Math.abs(direction - dir) != 2)
        next_direction = direction = dir;
}
function parse_input(input) {
    key = input[input.length - 1];
         if(key == "d") set_direction(3);
    else if(key == "w") set_direction(0);
    else if(key == "a") set_direction(1);
    else if(key == "s") set_direction(2);
    else if(key == " ") init();
}
function update() {
    if(alive)
        alive = update_snake();
}
alive = false;
this.getField("input").setFocus();
interval = app.setInterval("update()", gameSpeed);
) >>
>>}
}

\makeSnakeGame{}{}

\begin{document}

% The intro is draw behind the background, which gets overlayed when the game
% starts. Doing it this way around prevents the intro glitching out and not
% showing up. When the game starts everything gets refreshed and shows up.
\begin{textblock}{\boardSize}[0,0](0,0)
    \drawIntro
\end{textblock}

\begin{textblock}{\boardSize}[0,0](0,0)
    \begin{animateinline}[nomouse,label=intro]{1}
        \tikz{\path[use as bounding box] (0,0) rectangle (\gameSize,\gameSize);}
        \newframe \drawBackground
    \end{animateinline}
\end{textblock}

\foreach \i in {0,...,\gameSize-1}{
    \foreach \j in {0,...,\gameSize-1}{
        \animateCell{\i}{\j}
    }
}

% Initially the focus gets set to the first input field. When a key is pressed,
% the focus gets set to the second field, thereby updating the value attribute
% of the first field. The value is processed and the focus is set back to the
% first field.
\begin{textblock}{2}[0,12](0,0)
    \begin{Form}
        \TextField[width=1cm,name=input,keystroke={%
            this.getField("tmp").setFocus();
        }]{~}~%
        \TextField[width=1cm,name=tmp,onfocus={%
            parse_input(this.getField("input").value);
            this.getField("input").setFocus();
            this.dirty=false;
        }]{~}
    \end{Form}
\end{textblock}

% Click game area to set focus to first input field.
\begin{textblock}{\boardSize}[0,0](0,0)
    \mediabutton[jsaction={
        this.getField("input").setFocus();
    }]{%
        \begin{tikzpicture}
            \path[use as bounding box] (0,0) rectangle (\gameSize,\gameSize);
        \end{tikzpicture}
    }
\end{textblock}

\begin{textblock}{2}[-3.5,-8](0,0)
    \newcounter{score}
    \makeatletter
    \begin{animateinline}[nomouse,label=score]{1}
        \tikz{\path[use as bounding box] (0,0) rectangle (1,1) node[midway] {\huge ~};}
        \@whilenum\value{score}<64\do{\stepcounter{score}\newframe%
            \tikz{\path[use as bounding box] (0,0) rectangle (1,1)
                node[midway] {\huge \thescore};}%
        }
    \end{animateinline}
    \makeatother
\end{textblock}

\end{document}