HTML Snake Game

        <canvas id="gc" width="600" height="600"></canvas>
<script>
window.onload=function() {
    canv=document.getElementById("gc");
    ctx=canv.getContext("2d");
    document.addEventListener("keydown",keyPush);
    setInterval(game,1000/10);
    setInterval(superblocks,2000);
    setInterval(obstaclemove,4550);
}
px=py=13;
gs=20;
tc=30;
ax=Math.floor(Math.random()*tc);
ay=Math.floor(Math.random()*tc);
apx=Math.floor(Math.random()*tc);
apy=Math.floor(Math.random()*tc);
porx=Math.floor(Math.random()*tc);
pory=Math.floor(Math.random()*tc);
sx=Math.floor(Math.random()*tc);
sy=Math.floor(Math.random()*tc);
ox=Math.floor(Math.random()*tc);
oy=Math.floor(Math.random()*tc);
obx=Math.floor(Math.random()*tc);
oby=Math.floor(Math.random()*tc);
obsx=Math.floor(Math.random()*tc);
obsy=Math.floor(Math.random()*tc);
obstx=Math.floor(Math.random()*tc);
obsty=Math.floor(Math.random()*tc);
score=0;
highscore=0;
scoreten=false;
xv=yv=0;
trail=[];
tail = 4;
function game() {
    px+=xv;
    py+=yv;
    if(px<0) {
        tail = 4;
        xv=0;yv=0;
        px=13;py=13;
        if(score>highscore) {
            highscore=score;
        }
    }
    if(px>tc-1) {
        tail = 4;
        xv=0;yv=0;
        px=13;py=13;
        if(score>highscore) {
            highscore=score;
        }
    }
    if(py<0) {
        tail = 4;
        xv=0;yv=0;
        px=13;py=13;
        if(score>highscore) {
            highscore=score;
        }
    }
    if(py>tc-1) {
        tail = 4;
        xv=0;yv=0;
        px=13;py=13;
        if(score>highscore) {
            highscore=score;
        }
    }

    document.getElementById("score").innerHTML ="Score: " + score;
    document.getElementById("score").style.font = "bold 25px arial";

    document.getElementById("highscore").innerHTML ="Highscore: " + highscore;
    document.getElementById("highscore").style.font = "bold 20px arial";

    ctx.fillStyle="green";
    ctx.fillRect(0,0,canv.width,canv.height);

    ctx.fillStyle="lime";
    for(var i=0;i<trail.length;i++) {
        ctx.fillRect(trail[i].x*gs,trail[i].y*gs,gs-2,gs-2);
        if(trail[i].x==px && trail[i].y==py) {
            tail = 4;
            xv=0;yv=0;
            px=13;py=13;
            if(score>highscore) {
                highscore=score;
            }
        }
    }
    trail.push({x:px,y:py});
    while(trail.length>tail) {
    trail.shift();
    }
    if(ax==px && ay==py) {
        tail++;
        score++;
        ax=Math.floor(Math.random()*tc);
        ay=Math.floor(Math.random()*tc);
    }
    if(apx==px && apy==py) {
        tail++;
        score++;
        apx=Math.floor(Math.random()*tc);
        apy=Math.floor(Math.random()*tc);
    }
    ctx.fillStyle="red";
    ctx.fillRect(ax*gs,ay*gs,gs-2,gs-2);

    ctx.fillStyle="red";
    ctx.fillRect(apx*gs,apy*gs,gs-2,gs-2);

    if (px==porx && py==pory) {
        px=Math.floor(Math.random()*tc);
        py=Math.floor(Math.random()*tc);
        porx=Math.floor(Math.random()*tc);
        pory=Math.floor(Math.random()*tc);
    }

    ctx.fillStyle="white";
    ctx.fillRect(porx*gs,pory*gs,gs-2,gs-2);

    ctx.fillStyle="darkslategray";
    ctx.fillRect(ox*gs,oy*gs,gs-2,gs-2);

    ctx.fillStyle="darkslategray";
    ctx.fillRect(obx*gs,oby*gs,gs-2,gs-2);

    ctx.fillStyle="darkslategray";
    ctx.fillRect(obstx*gs,obsty*gs,gs-2,gs-2);

    ctx.fillStyle="darkslategray";
    ctx.fillRect(obsx*gs,obsy*gs,gs-2,gs-2);

    ctx.fillStyle="gold";
    ctx.fillRect(sx*gs,sy*gs,gs-2,gs-2);

    if(px==sx && py==sy) {
        tail++;
        tail++;
        score++;
        score++;
        sx=Math.floor(Math.random()*tc);
        sy=Math.floor(Math.random()*tc);
    }

    if(px==ox && py==oy) {
        tail = 4;
        xv=0;yv=0;
        px=py=13;
        if(score>highscore) {
            highscore=score;
        }
    }
    if(px==obsx && py==obsy) {
        tail = 4;
        xv=0;yv=0;
        px=py=13;
        if(score>highscore) {
            highscore=score;
        }
    }
    if(px==obx && py==oby) {
        tail = 4;
        xv=0;yv=0;
        px=py=13;
        if(score>highscore) {
            highscore=score;
        }
    }
    if(px==obstx && py==obsty) {
        tail = 4;
        xv=0;yv=0;
        px=py=13;
        if(score>highscore) {
            highscore=score;
        }
    }

    document.getElementById("credits").innerHTML ="Programmed by: Dario Casciato";
    document.getElementById("credits").style.font = "10px arial"

}
function keyPush(evt) {
    switch(evt.keyCode) {
        case 37:
            if(xv==0 && yv==0) {
                score=0;
            }
            xv=-1;yv=0;
            break;
        case 38:
            if(xv==0 && yv==0) {
                score=0;
            }
            xv=0;yv=-1;
            break;
        case 39:
            if(xv==0 && yv==0) {
                score=0;
            }
            xv=1;yv=0;
            break;
        case 40:
            if(xv==0 && yv==0) {
                score=0;
            }
            xv=0;yv=1;
            break;
        case 65:
            tail++;
            score++;
            break;
    }
}
function superblocks() {

    sx=Math.floor(Math.random()*tc);
    sy=Math.floor(Math.random()*tc);

}
function obstaclemove() {
    obstchoice=Math.floor(Math.random() * 4);
    obstachoice=obstchoice=Math.floor(Math.random() * 4);
    if(obstchoice==0) {
        if(obstachoice==0) {
            ox++;
        }
        if(obstachoice==1) {
            ox--;
        }
        if(obstachoice==2) {
            oy++;
        }
        if(obstachoice==3) {
            oy--;
        }
    }
    if(obstchoice==1) {
        if(obstachoice==0) {
            obx++;
        }
        if(obstachoice==1) {
            obx--;
        }
        if(obstachoice==2) {
            oby++;
        }
        if(obstachoice==3) {
            oby--;
        }
    }
    if(obstchoice==2) {
        if(obstachoice==0) {
            obsx++;
        }
        if(obstachoice==1) {
            obsx--;
        }
        if(obstachoice==2) {
            obsy++;
        }
        if(obstachoice==3) {
            obsy--;
        }
    }
    if(obstchoice==3) {
        if(obstachoice==0) {
            obstx++;
        }
        if(obstachoice==1) {
            obstx--;
        }
        if(obstachoice==2) {
            obsty++;
        }
        if(obstachoice==3) {
            obsty--;
        }
    }

}
</script>
<p id="score"></p>
<p id="highscore"></p>
<p id="credits"></p>