It had a very nice foliage atmosphere with very nice artwork and music.
The difficulty level was quite high even on Passable, and I had to give up on the strategy because I met an unprogressive bug in the middle of the game, but I enjoyed playing it.
I really like the special stage after the Noise Gauge has been built up, because it gives me a sense of tension.
And I felt that the disadvantages of Upgrade were bigger than the advantages, and I felt that it became more difficult after the upgrade, meow!