The simple mouse combat was really good, could there have been an area on the map that you needed to defend? It took me a little while to realise the game wasn't going to prompt me to make an upgrade and I needed to trigger them myself, I guess I was expecting something closer to a deckbuilder where I would play for acertain ammount of time/achieve a certain number of points/kills then the game would pause and present a few options for me to select from. Also the SFX got a bit chaotic after a while and over powered the music - I think the longer I played the less I cared about the single kill sounds and wanted to hear the music more.