Flappy Bird with Unity

Final project for codebar festival 2022 workshop.

Art assets from Freepik:

• Ground and icicle created by macrovector - www.freepik.com
• Bird created by freepik - www.freepik.com

Font from Google fonts:

• Fredoka One

Step-by-step:

Setup sprites

1. Open project
2. Drag bird_down sprite from Assets > Sprites to the FlappyScene hierarchy
3. Rename the object to Bird
4. Bring in the ground similarly, drag the position so that it's at the bottom
5. Modify camera to solid color instead of skybox
6. Set up sorting layers for sprites: obstacles, ground, bird & add sprites there, add bird & ground to correct layers

Setup colliders & first script

7. Add colliders to sprites: PolygonCollider2D for the bird, BoxCollider2D for the ground + adjust if necessary with edit mode
8. Add RigidBody2D to the bird game object
9. Create Bird script in the Scripts folder and add it to the Bird game object
10. Open script in VSCode by double clicking
11. Create isDead boolen variable and use that in the Update() method to check if the game is over or not
12. Create rb Rigidbody2D variable and get the RigidBody2D component to that in Start
13. Create a serialized float for upForce
14. In Update, with Input.GetMouseButton(0) check if the player has pressed the mouse button and

• set rb.velocity to zero to reset the velocity
• use rb.AddForce to add the force to the y coordinate

15. Get back to Unity, set upForce in the Inspector to 300, test if flapping works
16. Add Unity built-in OnCollisionEnter2D method to Bird.cs to check for collision with ground, and set isDead to true

Game over & score texts

17. Right-click in the hierarchy and create a Text game object from UI > Text – Text Mesh Pro
18. Import the TMP Essentials when suggested
19. Change the Canvas UI Scale Mode to Scale With Screen Size and use 1920 x 1080 as the reference resolution
20. The EventSystem game object won't be needed as we're not going to interact with UI, so delete that
21. Rename then the Text (TMP) game object to Score, set the text of it to Score: 0 and change the font to the one included in the project (Fredoka One)
22. Set the font size to a larger one, set the wrapping to disabled and align the text in the middle center
23. Set the anchor point on the Canvas (hold down Alt key in the anchor view), and lift the text up a bit so that's in a nice position at the bottom
24. Duplicate the Score game object with Ctrl+D (Cmd+D on macOS) and rename the duplicated one to GameOver, set the text to Game Over and the color to black
25. Anchor it to the top and adjust the y position to a nice position at the top
26. Duplicate the score text once more, rename it to FlapToRestart and set it as a child game object to the GameOver one
27. Set the text to "Flap to restart!", reset the y position and adjust it nicely below the game over text, and also decrease the font size a bit
28. Hide the GameOver GameObject from the checkbox in the Inspector

Game Controller

29. Create an empty GameObject by right-clicking in the hierarchy and selecting Create Empty, and name it GameController
30. Create GameController script in the Scripts folder and add it to the GameController game object
31. Create a method that handles the situation when the bird has died, birdDied in the GameController
32. Create a serialized GameObject for gameOverText
33. Set the gameOverText to active in the birdDied method
34. Create another serialized variable of type Bird for the bird script
35. Then make the Bird script's isDead variable a publicly gettable one (change to IsDead)
36. Start checking the bird's status in the game controller's Update method and call the birdDied method when the bird dies
37. Make a check that only calls the SetActive if the game object is not active already
38. Set the references to the script in Unity

Reloading the scene after game is over

39. Add a condition to game controller's Update method to check for player input when the bird is dead
40. Add needed using statement for UnityEngine.SceneManagement to be able to reload the scene
41. Add the scene reloading functionality to Update with SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex);

Background scrolling

42. Create ScrollingObject script in the Scripts folder and add it to the Ground game object
43. Add a RigidBody2D component to the Ground game object and set the type to Kinematic so that it's not affected by gravity and will only be moved from script
44. Create rb Rigidbody2D variable and get the RigidBody2D component to that in Start
45. Create a serialized float for scrollSpeed (talk about the setting the initial value and set it in the Inspector to -5)
46. Set the rb.velocity to the scroll speed in the x direction
47. Create a stopScrolling method for the scrolling object script
48. Create bird Bird variable and get the Bird script to that in Start via GameObject.Find
49. Call the stopScrolling method once the bird is dead
50. Create an empty game object in the hierarchy called Scenery, move the Ground underneath and duplicate the Ground two times (make sure that Scenery is at (0, 0, 0))
51. Move the first duplicate to the right by the amount indicator by the collider, and the second two times that
52. Create RepeatingBackground script in the Scripts folder and add it to the Ground game object
53. Create boxCollider BoxCollider2D variable and get the BoxCollider2D component to that in Start
54. Create length float variable and get the collider's length in x direction to that in Start
55. Create repositionBackground method and make the ground move to the left with an offset of length * 3
56. Check the position in Update and if in the x direction it's less than -length, then call the reposition method
57. Add the script to all ground game objects in the hierarchy

Obstacles

58. Drag icicle sprite from Assets > Sprites to the FlappyScene hierarchy
59. Rename the object to Icicle, scale and position it to the top part
60. Setup a PolygonCollider2D for the Icicle game object
61. Duplicate the Icicle game object, change the scale in y to negative and position nicely
62. Create an empty game object and call it Icicles, and move the two Icicles to its children
63. Add a BoxCollider2D to the Icicles game object and position it in the center of the two icicles, and set its Is Trigger on
64. Add a Rigidbody2D component to the Icicles game object and make it Kinematic
65. Create Icicles script in the Scripts folder and add it to the Icicles game object
66. Use OnTriggerEnter2D to detect collision between the scoring area and the bird
67. Add a public method SetScoreCallback that takes in an Action called scoreCallback and stores that in a variable called scoreCallback in the Icicles class
68. Add using System; to top for using Action
69. Call the scoreCallback when the bird scores
70. Add the ScrollingObject script to the Icicles game object
71. Create a Prefabs folder in the Project and then drag the Icicles game object there to create a prefab
72. Delete the prefab from the scene

Scoring callback

73. Add a method called birdScored to the game controller script and add there also a score variable that tracks the score
74. Add using TMPro; at the top and then create a serialized variable called scoreText of type TMP_Text and drag the score text object to that in the Inspector
75. Update the scoreText from the birdScored method

Icicle pooling

76. Create IciclePool script in the Scripts folder and add it to the GameController game object
77. Create a serialized GameObject for icilesPrefab
78. Create a serialized int for poolSize
79. Set the variables in the Inspector
80. Create an array of GameObjects in the IciclePool script to store the icicles and initialize it in Start with the poolSize
81. Add a variable poolPosition at (-50, -50)
82. Instantiate the icicle game objects to the array in Start with a loop
83. Add variables for spawnRate (can be serialized), timeSinceLastSpawned and a public variable Active
84. Update timeSinceLastSpawned in the Update method with Time.deltaTime
85. Create icicleIdx int variable to store the column index
86. Create spawnPositionX to control where the new columns are spawned
87. If timeSinceLastSpawned is larger than the spawn rate, set it to zero, create random y position for the next column and set the position of the current column to that
88. Lastly increase the icicleIdx and if it's larger than or equal to poolSize, set it back to zero
89. Add a public method SetScoreCallback that takes in an Action called scoreCallback and stores that in a variable called scoreCallback in the IciclePool class and add using System; to the top
90. Call the SetScoreCallback for each Icicle created in the Start by getting the Icicles component of the icicles[i] game object
91. Create an IciclePool variable for iciclePool in the game controller script get that in Start, and call its SetScoreCallback in Start to set the score callback to birdScored
92. Set the iciclePool.Active to false when the bird dies to stop the pool from recycling the icicles
93. Set the Script Execution Order in Edit > Project Settings so that GameController is executed before IciclePool to ensure that the callback is set correctly

Set up animations

94. Create an Animations Folder in Assets
95. Open Animation Window in Unity, select Bird game object and hit the Create button, name the animation Idle and save to Animations
96. Add property, expand Sprite Renderer category, add Sprite with the + add the bottom, and expand the sprite in the view
97. Delete second keyframe
98. Select the sprite by dragging over it, hit Ctrl+C (Cmd+C on macOS) to copy, select the Idle dropdown menu and select Create New Clip...
99. Save the new clip as Flap, hit Ctrl+V (Cmd+V on macOS) to paste
100. Hit the record button and then drag the bird_up sprite from the Project view to the Bird game object's Sprite Renderer
101. Open the Animator window, set up conditions for the animations:

• open the Parameters list on the list, create a Trigger parameter called Flap
• right-click on Idle, then Make Transition and drag it to Flap
• edit the transition by clicking on the arrow, remove Has Exit Time checkbox tick
• add the Flap trigger to the Conditions in the Inspector
• make a transition from Flap to Idle with Has Exit Time checked

102. Set the triggers from code:

• create anim Animator variable and get the Animator component to that in Start
• use anim.SetTrigger to change to the Flap state of the animator when the mouse button is pressed