Mediocre
I really enjoyed the other Sentinel games, but this one is mediocre at best. Its not well balanced, and the enemies that can damage turrets get very powerful very quickly. For $5 I would expect it to be balanced, and not need to buy in app boosts to make the turrets useful.
Also, whoever made the sound effects should be fired! The monster death sounds, and many others, are terrible, and sound like they would be at home on an Atari 2600.
Needs more polish to be worth it. Kingdom rush is much, much better if you want a TD game to play.
Graysdir about
Sentinel 4: Dark Star, v1.0.0