Additions

The game now has a proper app icon, instead of the default processing one.
When hovering a defence on the defence selection UI, a new tooltip is shown which displays details about the defence, including damage, range, and speed for towers. This tooltip is now also used to display repair cost, and let you know when something is too expensive.
You can now hover the central castle to display a tooltip showing it's exact health value, along with some info.
You can now see which wave you are currently on while the wave is running.
You can now press F3 to activate the debug menu (Previously it could only be turned on by editing the code).
When hovering a defence on the grid, it is now outlined in white as well as tinted red to address colourblind accessibility issues with using only a red tint.

Tweaks

If the window size is too small, the wave start and show tutorial buttons will now move out of the way instead of overlapping the defence selection UI.
The game is now rendered at a pixel density of 1, which should make it perform better on macOS & high-dpi displays.
Removed most of the details, such as tower damage, from the defence selection UI (These details are now shown in a tooltip on hover).
Slightly tweaked some UI transparency.
The grid that appears when placing defences and the tower range circle are now more opaque.
The difficulty of the game has been tweaked in a variety of ways. It is now slightly more difficult.

The game now runs in windowed mode, which fixes an issue with the bottom of the screen being cut off on macOS.
Fixed an issue where the app would ask for permission to use the microphone on macOS. This was a quirk of the library I was using to play sound, and I have now switched to a different library.
If you place defences on the very edge of the buildable area, enemies will no longer sometimes get stuck on it and crash the game.