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<!--------------------------------------------------------------------------------------------->
Relates to https://github.com/excaliburjs/Excalibur/issues/3627
## Changes:
Updated flappy bird tutorial with a note regarding expected behavior of bug when the bird dies.
Updated flappy bird tutorial code snippets to include a few missing imports.
Documentation Updates:
Step 4 of flappy bird tutorial (https://excaliburjs.com/docs/step-4-flying-bird)
Before
<img width="1382" height="748" alt="Screenshot 2025-12-19 at 12 24 33 PM" src="https://github.com/user-attachments/assets/2c2ad3d1-7382-4c84-812a-87c6a03f437a" />
After
<img width="1342" height="659" alt="Screenshot 2025-12-19 at 12 23 30 PM" src="https://github.com/user-attachments/assets/d56682f8-e912-4a3f-bb60-6203ff9eba66" />
Step 8 of flappy bird tutorial (https://excaliburjs.com/docs/step-8-periodic-pipes)
Before
<img width="1413" height="786" alt="Screenshot 2025-12-19 at 12 26 15 PM" src="https://github.com/user-attachments/assets/b7551333-f5e0-4c30-9bf5-f2b08cd89257" />
After
<img width="1054" height="390" alt="Screenshot 2025-12-19 at 12 23 55 PM" src="https://github.com/user-attachments/assets/adb006dc-59aa-447f-85a1-222de52df07e" />
Step 9 of flappy bird tutorial (https://excaliburjs.com/docs/step-9-scoring-points)
Before
<img width="1109" height="725" alt="Screenshot 2025-12-19 at 12 27 33 PM" src="https://github.com/user-attachments/assets/33ff6c43-af87-4883-b062-c44258a35b65" />
After
<img width="1070" height="297" alt="Screenshot 2025-12-19 at 12 24 02 PM" src="https://github.com/user-attachments/assets/9f2d1cdb-1401-428e-b1db-7817820a77e0" />
Signed-off-by: Scott Westover <swestover@manh.com>