Broken friction

[7Bpencil]

you define friction as:
obj.Velocity -= Friction * dt;

this is the same as:
ob.Velocity.X -= Friction * dt;
ob.Velocity.Y -= Friction * dt;

So it means if vector component is negative (or zero), it's absolute value increases. It's clearly visible when objects with zero velocity slowly move to the bottom left corner (or top left - depends on coordinate system).

[7Bpencil]

I used this

var friction = Friction * dt;
PhysMath.RoundToZero(ref velocity, tolerance);
velocity.X += velocity.X == 0 ? 0 : velocity.X > 0 ? -friction : friction;
velocity.Y += velocity.Y == 0 ? 0 : velocity.Y > 0 ? -friction : friction;

[7Bpencil]

Or this:
velocity -= Vector2.Normalize(velocity) * friction;

[dankelley2]

Fixed in latest commit