Faster and Faster

Lesson 13 of 14 in Coddy's Unity Game: Snake 3D course.

Snake gets harder as it grows: each food makes the tick a little shorter, so the snake steps faster. A floor keeps the game playable: the shortest tick it may reach.

Mathf.Max returns the larger of two numbers, which makes it a floor: Mathf.Max(value, floor) is never below floor. A turret that fires faster with each upgrade, but never more often than every 0.2 seconds:

cooldown = Mathf.Max(cooldown - 0.05f, 0.2f);

Mathf.Min is the opposite, a ceiling. Mixing them up is an easy slip: with Min, the cooldown above would drop to 0.2 at the first upgrade. The timer in Update() reads tick on every frame, so a shorter tick counts from the next step on.

Challenge

Hard

Add public float speedUp = 0.005f; and public float minTick = 0.08f; to Snake.
When the snake eats, make tick shorter by speedUp, but never shorter than minTick.

Press Play and eat: the snake speeds up. Then press Check.

Try it yourself

using System.Collections.Generic;
using UnityEngine;
using UnityEngine.InputSystem;

public class Snake : MonoBehaviour
{
    public float tick = 0.15f;   // seconds between two steps
    public int edge = 7;         // the board's cells run from -edge to edge
    public bool alive = true;
    public List<Transform> tail = new List<Transform>();
    public Transform segmentPrefab;
    private float timer;
    private Vector3 direction = Vector3.right;       // the way the head moved on its last step
    private Vector3 nextDirection = Vector3.right;   // the turn waiting for the next step

    void Update()
    {
        if (!alive) return;

        Keyboard keyboard = Keyboard.current;
        if (keyboard != null)
        {
            if (keyboard.upArrowKey.wasPressedThisFrame || keyboard.wKey.wasPressedThisFrame) Turn(Vector3.forward);
            if (keyboard.downArrowKey.wasPressedThisFrame || keyboard.sKey.wasPressedThisFrame) Turn(Vector3.back);
            if (keyboard.leftArrowKey.wasPressedThisFrame || keyboard.aKey.wasPressedThisFrame) Turn(Vector3.left);
            if (keyboard.rightArrowKey.wasPressedThisFrame || keyboard.dKey.wasPressedThisFrame) Turn(Vector3.right);
        }

        timer += Time.deltaTime;
        if (timer >= tick)
        {
            timer -= tick;
            Step();
        }
    }

    void Turn(Vector3 newDirection)
    {
        if (newDirection != -direction)
        {
            nextDirection = newDirection;
        }
    }

    void Step()
    {
        direction = nextDirection;
        Vector3 next = transform.position + direction;
        if (Mathf.Abs(next.x) > edge || Mathf.Abs(next.z) > edge)
        {
            Die();
            return;
        }

        for (int i = 0; i < tail.Count - 1; i++)
        {
            if (tail[i].position == next)
            {
                Die();
                return;
            }
        }

        Vector3 tailEnd = tail.Count > 0 ? tail[tail.Count - 1].position : transform.position;
        for (int i = tail.Count - 1; i > 0; i--)
        {
            tail[i].position = tail[i - 1].position;
        }
        if (tail.Count > 0)
        {
            tail[0].position = transform.position;
        }
        transform.position = next;

        if (GameManager.Instance.IsFood(next))
        {
            tail.Add(Instantiate(segmentPrefab, tailEnd, Quaternion.identity));
            GameManager.Instance.Eat();
        }
    }

    public bool Occupies(Vector3 cell)
    {
        if (transform.position == cell) return true;
        foreach (Transform segment in tail)
        {
            if (segment.position == cell) return true;
        }
        return false;
    }

    void Die()
    {
        alive = false;
        GameManager.Instance.GameOver();
    }
}