gistfile1.txt

// motion_add(dir, spd):

vx += spd * cos(dir);
vy -= spd * sin(dir);

// setting speed to spd:

var current_speed;
current_speed = sqrt(vx*vx + vy*vy);
vx *= spd / current_speed;
vy *= spd / current_speed;

// friction:

var current_speed;
current_speed = sqrt(vx*vx + vy*vy);

if (current_speed > fric) {
  vx *= (current_speed - fric) / current_speed;
  vy *= (current_speed - fric) / current_speed;
} else if (current_speed < -fric) {
  vx *= (current_speed + fric) / current_speed;
  vy *= (current_speed + fric) / current_speed;
} else {
  vx = 0;
  vy = 0;
}