Free Unity C# Cheat Sheet (Printable PDF)

🔄 MonoBehaviour Lifecycle

void Awake() {
    // runs on object creation
}

void OnEnable() {
    // runs when object becomes active
}

void Start() {
    // runs before first frame
}

void Update() {
    // runs every frame
}

void FixedUpdate() {
    // runs on physics step (50 Hz)
}

void LateUpdate() {
    // runs after all Update calls
}

void OnDisable() {
    // runs when object deactivated
}

void OnDestroy() {
    // runs when object destroyed
}

⌨️ Input

Input.GetKey(KeyCode.A)	Held down
Input.GetKeyDown()	Pressed this frame
Input.GetKeyUp()	Released this frame
Input.GetAxis("Horizontal")	-1 to 1 smoothed
Input.GetAxisRaw()	-1 or 1 no smoothing
Input.GetButton("Jump")	Virtual button held
Input.GetButtonDown()	Virtual button pressed
Input.GetMouseButton(0)	Left mouse held
Input.GetMouseButtonDown(0)	Left click this frame
Input.mousePosition	Mouse screen position
Input.touchCount	Number of touch points
Input.GetTouch(0)	Touch data by index

⚡ Physics

Rigidbody2D / Rigidbody	Physics body component
AddForce(Vector2)	Apply force to rigidbody
rb.linearVelocity	Current velocity vector (Unity 6)
Physics2D.Raycast()	2D ray collision test
Physics.Raycast()	3D ray collision test
OnCollisionEnter2D()	2D collision callback
OnTriggerEnter2D()	2D trigger callback
OnCollisionEnter()	3D collision callback
OnTriggerEnter()	3D trigger callback
rb.isKinematic	Disable physics simulation

🧩 Components

// Get existing component
var rb = GetComponent<Rigidbody2D>();

// Find in children
var sr = GetComponentInChildren<SpriteRenderer>();

// Add new component
var col = AddComponent<BoxCollider2D>();

// Spawn prefab
var obj = Instantiate(prefab, position, rotation);

// Remove object
Destroy(gameObject);
Destroy(gameObject, 2f);  // delayed

// Find by name / tag
GameObject.Find("Enemy");
GameObject.FindWithTag("Player");
GameObject.FindGameObjectsWithTag("Coin");

🎨 UI

Text (TMP)	Text display component
Image	Sprite/image display
Button	Clickable UI button
Slider	Value slider (0-1)
InputField	Text input box
Canvas	Root UI container
RectTransform	UI positioning/sizing
CanvasGroup	Fade/show/hide UI block
ScrollRect	Scrollable content area

// Update text
GetComponent<TextMeshProUGUI>().text = "Score: " + score;

// Fade out UI
canvasGroup.alpha = 0f;
canvasGroup.interactable = false;

⏳ Coroutines

using System.Collections;

IEnumerator SpawnWave() {
    yield return new WaitForSeconds(2f);
    Instantiate(enemy, spawnPos, Quaternion.identity);
    yield return null;  // wait one frame
    yield return new WaitUntil(() => ready);
    yield return new WaitWhile(() => !ready);
}

// Start / Stop
StartCoroutine(SpawnWave());
StopCoroutine(SpawnWave());
StopAllCoroutines();

🎬 Scene Management

using UnityEngine.SceneManagement;

// Load scene
SceneManager.LoadScene("Level2");
SceneManager.LoadScene(1);  // by build index

// Async load
var op = SceneManager.LoadSceneAsync("Level2");
yield return op;

// Reload current scene
SceneManager.LoadScene(
    SceneManager.GetActiveScene().buildIndex);

// Quit app
Application.Quit();

// Application focus / pause
Application.targetFrameRate = 60;

🧮 Math

Vector2(x, y)	2D vector
Vector3(x, y, z)	3D vector
Mathf.Lerp(a, b, t)	Linear interpolation
Mathf.Clamp(val, min, max)	Restrict to range
Mathf.Abs(n)	Absolute value
Mathf.Pow(b, e)	Power / exponent
Mathf.Sqrt(n)	Square root
Mathf.Round(n)	Round to nearest int
Quaternion.Euler(x, y, z)	Euler to rotation
Vector3.Distance(a, b)	Distance between points

🛠️ Common Patterns

── PLAYER CONTROLLER (2D) ──
float speed = 5f;
float jumpForce = 10f;
Rigidbody2D rb;

void Start() {
    rb = GetComponent<Rigidbody2D>();
}

void Update() {
    float move = Input.GetAxisRaw("Horizontal");
    rb.linearVelocity = new Vector2(move * speed, rb.linearVelocity.y);

    if (Input.GetKeyDown(KeyCode.Space) && Mathf.Abs(rb.linearVelocity.y) < 0.01f)
        rb.AddForce(Vector2.up * jumpForce, ForceMode2D.Impulse);
}

── CAMERA FOLLOW ──
Transform target;
float smoothSpeed = 0.125f;

void LateUpdate() {
    var pos = new Vector3(target.position.x, target.position.y, transform.position.z);
    transform.position = Vector3.Lerp(transform.position, pos, smoothSpeed);
}

── HEALTH SYSTEM ──
public int maxHealth = 100;
int currentHealth;

public void TakeDamage(int amount) {
    currentHealth -= amount;
    if (currentHealth <= 0) {
        Die();
    }
}

── SPAWNING ──
public GameObject prefab;
public float spawnRate = 2f;

void Start() { InvokeRepeating("Spawn", 0f, spawnRate); }

void Spawn() {
    Instantiate(prefab, new Vector3(0, 7, 0), Quaternion.identity);
}

── SAVE SYSTEM ──
PlayerPrefs.SetInt("Score", score);
int s = PlayerPrefs.GetInt("Score");
PlayerPrefs.SetString("PlayerName", name);
PlayerPrefs.Save();

Unity C# Cheat Sheet

🔄 MonoBehaviour Lifecycle

⌨️ Input

⚡ Physics

🧩 Components

🎨 UI

⏳ Coroutines

🎬 Scene Management

🧮 Math

🛠️ Common Patterns

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