How to Make Combat Fun?

Combat system is single most important mechanic in the game. It absolutely needs to be fun. But fun as a term itself doesn't mean anything. This post is unusually long and no part of this design is in "finalized" form, anything mentioned here might change as a result of iteration or player feedback. Here's my plan for making exciting combat:

Goal: Combat that's easy to learn and simple to use but allows flexible maneuvers in more complex combat situations.

Plan to reach the goal: Easy controls for attacks, but effective use depends on strategy you apply for different enemy types and situations. 

* Hit attack can be performed towards one of the 4 directions. Melee hits consume the same energy force field is using so attacking makes you more vulnerable. Simultaneously each melee hit after another is more powerful, downside naturally is that you can't move while you are attacking so you are more likely to get hit as well.

* Shared resource between protection and combat moves. You need to balance between defense and offense. If not consumed the energy keeps charging back. Moving from cover to cover might allow you to keep up your energy levels for initial melee encounter.

* Running in combat armor also consumes energy, but allows for faster movement and hit done while running is powerful blow that stuns your enemy, however the hit eats about fourth of your energy instantly, so less is left for combat situations after.    

* Every new enemy type is also a new type of combat situation, sort of an "action puzzle". When combined to same combat situation the various combat challenges different types offer should offer synergy. For instance one enemy type might slow you down while another shoots all around. Alone enemy that just slows is easy to defeat and with enemy that shoots around you can dodge, but if you are being slow and can't dodge then a shooter might have easier time hitting you. 

*  Enemies change visually when they are damaged, so you don't need UI element for enemy status. All that is visible is your own

* Module brings one special ability as addition to hitting and running that always has weakness at certain type of enemy types and strengths against others. 

Goal:  Combat is juicy and feels powerful

Plan to reach the goal: Hits need to connect and feel juicy, combat animations need to look powerful and sound effects need to be buff. With hits comes small effects like slight camera shake and getting damage on force field shakes camera too. After damage has reached your inner armor the shake is more severe and closer you are death more red-tinted the screen turns into and it's also harder to see. When enemies are damaged there are several indicators for this:

* Slight camera shake
* Getting hit audio clip
* Enemy has getting hit animation
* As addition enemy flashes with red tint (alternative: blood)
* Slight rumble in controller

Making the combat feel juicy audio and animations play a huge role. There should be same audioclip for getting damaged for every enemy so the connection is an instant one.