How do I make a jetpack stain the floor with pixels?

My suggestion would be to create a particle system for the pixels flying out of the back. As for the stains on the ground, you'd probably have to place a sprite flat on the ground, by first raycasting downwards, and then getting the normal of the face that you collided with:

public GameObject Splatter; //Object to use as splatter effect public void Splat(){ RaycastHit hit; if(Physics.Raycast(transform.position, -transform.up, out hit, 5)){ // checks below to see if there is an object within 5 units. GameObject SplatStain = (GameObject)Instantiate (Splatter, hit.point, Quaternion.identity); //creates a splatter at the point where the raycast hit SplatStain.transform.LookAt (hit.point + hit.normal); //faces it looking outwards SplatStain.transform.localRotation = Quaternion.Euler (0, Random.Range (0, 360), 0); //randomizes its rotation to make it look less uniform } }

all you have to do is run 'Splat()' every time you want it to splatter, and you should be good! If you want to add some randomization to the direction of the raycast, then it might make it look even less uniform, which is nice.

Hope that helps!