Speed up/Slow down an object once it collides with an object - xna

Question

I'm currently working on a 2D platformer and I'm wondering if I can get any tips on how to increase the speed that an object moves at for a few seconds after it collides with another object.

Answer 1

First you need a variable called velocity
Vector2 velocity = new Vector2(0.0f, 0.0f);
Every update, you change the Rectangle of the sprite by the velocity.
rectangle.X += (int)velocity.X;
rectangle.Y += (int)velocity.Y;
Then, you can change the velocity however you like and it will change the speed.
//slow down
velocity.X -= 10;
velocity.Y -= 10;
//speed up
velocity.X += 10;
velocity.Y += 10;
You can also change the X and Y values for velocity individually, like this:
velocity.Y += 10;
That will make the sprite move down when typed in.
Hope this helped! Tell me if you need any clarification!

Answer 2

First you want to have it react to the collision, so in the method you're using to detect the collision, add a call to a new method in your object. Let's call it SpeedUp(). It should look something like this:
public void SpeedUp()
{
_speedUpTimer = 0;
IsSpedUp = true;
_maxVelocity.X = SpedUpVelocity.X;
}
where _speedUpTimer is a variable in your object's class (or whatever component handles movement), _maxVelocity is whatever variable maintains your object's top speed, and SpedUpVelocity is the constant or variable holding the faster velocity. IsSpedUp should be initialized as false. You're also going to want a constant or variable to hold the amount of time you want the object to be faster, such as SpeedUpTime.
Then, in your object's Update(), add the lines
_speedUpTimer += gameTime.ElapsedGameTime.Milliseconds;
if (IsSpedUp && _speedUpTimer > SpeedUpTime)
{
_maxVelocity.X = UsualMaxVelocity.X;
IsSpedUp = false;
}
UsualMaxVelocity will hold your object's previous, non-sped-up maximum velocity, which your object will return to using after the timer is up.
Of course, you can always make your Y velocity increase, but I assumed you just wanted horizontal speed.