prova così crei il tuo clip

lo selezioni e gli apllichi questo:

codice:
onClipEvent (load) { 
xSpeed = 0; 
ySpeed = 0; 
thrust = 3; 
decay = 0.90; 
maxSpeed = 15; 
} 
onClipEvent (enterFrame) { 
if (Key.isDown(Key.RIGHT)) { 
xSpeed += thrust*Math.cos(Math.PI/180); 
} else { 
xSpeed *= decay; 
} 
if (Key.isDown(Key.LEFT)) { 
xSpeed -= thrust*Math.cos(Math.PI/180); 
} else { 
xSpeed *= decay; 
} 
if (Key.isDown(Key.UP)) { 
ySpeed += thrust*Math.cos(Math.PI/180); 
} else { 
ySpeed *= decay; 
} 
if (Key.isDown(Key.DOWN)) { 
ySpeed -= thrust*Math.cos(Math.PI/180); 
} else { 
ySpeed *= decay; 
} 
speed = Math.sqrt((xSpeed*xSpeed)+(ySpeed*ySpeed)); 
if (speed>maxSpeed) { 
xSpeed *= maxSpeed/speed; 
ySpeed *= maxSpeed/speed; 
} 
_y -= ySpeed; 
_x += xSpeed; 
}