# Help: Issue downloading .uf2 for handheld - "Program Error: unhandled exception"

**URL:** https://forum.makecode.com/t/help-issue-downloading-uf2-for-handheld-program-error-unhandled-exception/40629
**Category:** Help
**Created:** [November 24, 2025, 3:54am UTC](https://forum.makecode.com/t/help-issue-downloading-uf2-for-handheld-program-error-unhandled-exception/40629 "2025-11-24T03:54:47Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![DionTsang](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.makecode.com/diontsang/32/26852_2.png) [@DionTsang](https://forum.makecode.com/u/DionTsang)
#### Post date: [November 24, 2025, 3:54am UTC](https://forum.makecode.com/t/help-issue-downloading-uf2-for-handheld-program-error-unhandled-exception/40629/1 "2025-11-24T03:54:47Z")

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Hi everyone,

I’m hoping someone can help identify an issue we are having with a project [Fossil Clicker](https://forum.makecode.com/t/fossil-clicker-my-prehistoric-game-jam-submission/21524).

We are planning to download the game file so that we can play it on Meowbit later. The game runs smoothly in the browser simulator, while we tried to download: the game malfunctions and displays a message that says **‘wrong uses’** or **‘Program Error: unhandled exception: Not implemented.’**

Because of this, we are unable to download the .uf2 files.

We’re not sure whether this is a problem with the specific code or the Arcade game development platform itself. Do you happen to know the cause?

Attach is screenshot of the errors.

 ![image](https://us1.discourse-cdn.com/flex020/uploads/makecode/original/3X/2/a/2ad223a359a35640c845384f4d6483bbd9de88e9.png)

Looking forward to your reply, thank you!

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### Author: ![AlexK](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.makecode.com/alexk/32/33339_2.png) [@AlexK](https://forum.makecode.com/u/AlexK)
#### Post date: [November 24, 2025, 3:56am UTC](https://forum.makecode.com/t/help-issue-downloading-uf2-for-handheld-program-error-unhandled-exception/40629/2 "2025-11-24T03:56:21Z")

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Press F12 to open the browser tools (or use the equivalent for your browser). Open the Console tab to view errors produced during compilation.

It shows that there is a problem with the **BetterSettings** extension when compiling for the MeowBit. That extension appears to be incompatible with the MeowBit.

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### Author: ![UnsignedArduino](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.makecode.com/unsignedarduino/32/592_2.png) [@UnsignedArduino](https://forum.makecode.com/u/UnsignedArduino)
#### Post date: [November 24, 2025, 5:31am UTC](https://forum.makecode.com/t/help-issue-downloading-uf2-for-handheld-program-error-unhandled-exception/40629/3 "2025-11-24T05:31:17Z")

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I’ve also responded in an email with Dion about the “not implemented error”, which comes from my loading animation extension when trying to compile for hardware. (so remove the opening splash to fix that) For some reason, the overridden method which works in the browser doesn’t do anything when compiling for hardware.

But…removing that leads to more errors so 🤷‍♂️