Over time, there will be very small popping sounds.

• You can play them publicly or increase the volume.
• If you like quietness, you can also turn off the music playback of the game, and then navigate to the game download folder separately to open the game audio file in the same path. The effect is basically the same as opening the background music in the game.

The game may not currently support saving, but this may not be a compatibility or network issue, but rather the game itself can be freely selected. You just need to remember the level number and name.

But in case you really forget where to play, there is a weapon icon in the bottom right corner of the UI selection box for each level that thoughtfully marks the unlocking progress of the corresponding attacking unit in the game.