I liked the mechanic of the game, the art and sounds(music and sound effects), The shop are so awesome, but there are some problems like:
1- the game is unbalancing (player health is so low and weapons are also unbalancing), I suggest making the medkit cheaper than in the game, making the weapons strong, weapons to be less than in the game, and making enemies bullet weak.
2- the progress of the game is slow.
But overall I loved the game :)