Hi there! Thanks for reaching out. I understand the Word Trip app is running really slow when you're trying to select letters for a word on your iPhone with iOS 18.7. I want to help you get this sorted out smoothly.

To start, can you tell me a bit more about when the slowdown happens? For example:
- Does it happen every time you open the app or only in certain puzzles?
- Are other apps on your phone running fine, or is the device overall slow?
- Have you tried restarting your phone already or closing and reopening the Word Trip app?

Meanwhile, here are some steps we can try to improve the performance:

1. Restart Your iPhone
Restarting can clear temporary glitches and refresh your system. Press and hold the side button and either volume button, then slide to power off. Turn it back on after a minute.

2. Force Quit and Relaunch Word Trip
Swipe up from the bottom of the screen and pause in the middle (on iPhone with no home button) to open app switcher. Swipe the Word Trip app up to close it, then open it again.

3. Clear App Data / Reinstall Word Trip
Sometimes local data gets cluttered. You can uninstall the app by pressing and holding its icon until it jiggles, then tap the X to delete. Re-download it from the App Store. Note that this will reset your progress unless your account syncs with cloud.

4. Close Background Apps
Too many apps running in background can slow device responsiveness. Try closing apps you're not using.

5. Check for iOS and App Updates
Make sure your iOS 18.7 is fully updated (Settings > General > Software Update) and that Word Trip is the latest version in the App Store.

If after these steps the problem persists, it might be related to app-specific issues or compatibility with iOS 18.7. In that case, I can help you check if there are any known ongoing issues or more advanced troubleshooting options.

Could you please let me know what you've already tried or noticed? That way I avoid repeating steps and can guide you better.

Looking forward to your reply!