int W = 40;
int H = 25;
int SQ = 10;

boolean timeToDie;

Walker w = new Walker();

color DARK = color(0, 0, 128);
color LIGHT = color(100, 100, 100);

int screen[][] = new int[W][H];
color wallcolor[][] = new color[W][H];

void setup() {
size(400,250);  
  background(DARK);
  frameRate(100);
  size(W*SQ, H*SQ); 
  strokeWeight(4);

  for (int x = 0; x < W; x++) {
    for (int y = 0; y < H; y++) {
      screen[x][y] = round(random(1));
      wallcolor[x][y] = LIGHT;
      drawSlash(x,y);

    }
  }
}
int DOWNSLASH = 0;
int UPSLASH = 1;


void mouseReleased() {
  timeToDie = true;
}


void draw() {
   
  if(w != null){
  w.drawWall();
  
  if(timeToDie){
     w = new Walker();
    timeToDie = false; 
  }
  
  w.move();
  w.draw();
  if(w.markAndCheckForLoop()){
    timeToDie = true;
  }
  }
}


void drawSlash(int x, int y){
  noStroke();
  fill(DARK);
  rect(x * SQ, y*SQ,SQ,SQ);
   stroke(wallcolor[x][y]);
      if (screen[x][y] == DOWNSLASH) {
        line(x * SQ, y*SQ, (x+1)*SQ, (y+1)*SQ);
      } 
      else {
        line(x*SQ, (y+1)*SQ, (x+1)*SQ, y*SQ);
      } 
}

int LEFT = 1;
int RIGHT = 2;
int UP = 3;
int DOWN = 4;
class Walker {
  int x, y;
  int godir;
  color c;
  
  int myhist[][] = new int[W][H];
  
  Walker() {
    x =  floor(random(W));
   y = floor(random(H));

//x = mouseX / SQ;
//y = mouseY / SQ;

    godir = floor(random(4))+1;
    c = color(128+random(128), 128+random(128), 128+random(128));
  }



  void move() {
    int revx = x;
    int revy = y;
    int revdir = -1;
    if (godir == LEFT) {
      x -= 1; revdir = RIGHT;
    }
    if (godir == RIGHT) {
      x += 1; revdir = LEFT;
    }
    if (godir == UP) {
      y -= 1; revdir = DOWN;
    }
    if (godir == DOWN) {
      y += 1; revdir = UP;
    }
    if (x < 0 || x  >= W || y < 0 || y >= H) {
      x = revx;
      y = revy;
      godir = revdir;
    } 
    
      bounce();
// println(":::"+godir);
 }
int score = 0;
  boolean markAndCheckForLoop(){
    //if(wallcolor[x][y] == LIGHT) {
        wallcolor[x][y] = c;
         score++;  
    //} 
    //only mark first doreciton this way...
    if(myhist[x][y] == 0) myhist[x][y] = godir;
    else { 
      //if seen before, see if we saw it in this direction...
      if(godir == myhist[x][y]){
         drawWall();
        //println(score);
        return true;  
      }
  
  }
    
    return false;
  }

  void bounce() {
    if (godir == RIGHT) {
      if (screen[x][y] == UPSLASH) godir = UP;
      else godir = DOWN; 
      return;
    }
    if (godir == LEFT) {
      if (screen[x][y] == UPSLASH) godir = DOWN;
      else godir = UP; 
      return;
    }
    if (godir == UP) {
      if (screen[x][y] == UPSLASH) godir = RIGHT;
      else godir = LEFT; 
      return;
    }
    if (godir == DOWN) {
      if (screen[x][y] == UPSLASH) godir = LEFT;
      else godir = RIGHT; 
      return;
    }

    return;
  }

  void drawWall(){
    drawSlash(x,y);
  }
  void draw() {
    noFill();   
    stroke(c);

    ellipse((x+.5)*SQ, (y+.5)*SQ, SQ/2, SQ/2);
  }
}