Three Lanes

Part of the Building Real Games section of Coddy's Unity journey. Lesson 27 of 56.

This chapter builds an Endless Runner. A runner races down a road of three lanes and switches lanes to dodge the obstacles that come toward it. Over the next lessons the road speeds up, the distance shows on screen, a crash ends the run with a button to run again, and the best run is saved. The runner never moves forward: it stays at z = 0 and the obstacles travel toward it, so the road never runs out. The game has four scripts, Runner, Spawner, Obstacle and GameManager, and the last three are empty for now.

A runner in lanes is not steered like a car: it is always in one of a few places. Keep the place as a whole number, change the number on a key press, and work out the position from it. This window cleaner's platform serves the five floors of a building, 3 units apart:

[SerializeField] private float floorHeight = 3f;
[SerializeField] private float moveSpeed = 6f;
private int floor = 0;

void Update()
{
    if (Input.GetKeyDown(KeyCode.UpArrow)) floor++;
    if (Input.GetKeyDown(KeyCode.DownArrow)) floor--;
    floor = Mathf.Clamp(floor, 0, 4);

    Vector3 p = transform.position;
    p.y = Mathf.MoveTowards(p.y, floor * floorHeight, moveSpeed * Time.deltaTime);
    transform.position = p;
}

GetKeyDown makes one press one floor, where GetKey would add a floor on every frame the key is held. Mathf.Clamp keeps the number on the building, so up on the top floor does nothing, and the next press down goes straight to floor 3. Mathf.MoveTowards slides the platform toward its floor at moveSpeed units a second and stops exactly on it, instead of jumping there in one frame. The position is a copy, changed and assigned back, because transform.position.y cannot be set on its own.

Challenge

Medium

Start the Endless Runner with the runner. The Inspector gives Runner a laneWidth of 2.5 and a laneSpeed of 15, and lane is -1 for the left lane, 0 for the middle and 1 for the right. In Runner's Update():

Each press of the left or right arrow changes lane by one, that way. Holding the key still changes it by one.
lane never goes below -1 or above 1.
The runner slides along x to lane * laneWidth at laneSpeed units per second, and keeps its y and z.

Leave the other three scripts as they are for now. Press Play, click the game and switch lanes, then Check.

Try it yourself

using UnityEngine;

public class Runner : MonoBehaviour
{
    public float laneWidth = 2.5f;
    public float laneSpeed = 15f;
    private int lane = 0;   // -1 is the left lane, 0 the middle, 1 the right

    void Update()
    {
        // Change lanes with the arrows, then slide toward the lane's x
    }
}