var v = document.getElementById("v").getContext("2d");
v.fillStyle="rgba(0,0,123,1.0)";

var x = 250;
var y = 250;

var az = document.getElementById("az");
var angle = 235;


setInterval('move()', 5);


function move(){
    
    v.fillStyle="rgba(255,255,255, 1.0)";
    v.fillRect(x-2, y-2, 8, 8);
    
    x +=  Math.sin(angle * Math.PI/180.0)*1.0;
    y +=  Math.cos(angle * Math.PI/180.0)*1.0; 
    
    v.fillStyle="rgba(0,0,123,1.0)";
    v.fillRect(x, y, 5, 5);

    angle = getNewAngle(angle);
    
    az.innerHTML = angle + " " + parseInt(x) + " " + parseInt(y);
}

function getNewAngle(actAngle){
    var newAngle=actAngle;
    if(x>400){ //jobb fal    
        if(actAngle < 180 && actAngle > 90)
            newAngle = actAngle + 90;
        if(actAngle < 90 && actAngle > 0){
            newAngle = actAngle - 90;
            if(newAngle <0)
                newAngle = 360 + newAngle;
        }
    }
    if(x<=5){ //bal fal
        if((actAngle > 270) && (actAngle < 360)){
            newAngle = actAngle + 90;
            if(newAngle>360)
                newAngle = newAngle - 360;
        }
        if((actAngle > 180) && (actAngle < 270)){
            newAngle = actAngle - 90;           
            
        }
    }
    if(y<0){
        if((actAngle>180) && (actAngle < 270)){
            newAngle = actAngle + 90;
        }
        if((actAngle<180) && (actAngle > 90)){
            newAngle = actAngle - 90;
        }
    }
    if(y>400){
        if(eval(actAngle) > 270 && eval(actAngle) < 360)
            newAngle = actAngle - 90;
        if(actAngle > 0 && actAngle < 90)
            newAngle = actAngle + 90;
    }    
    return newAngle;
}