Hi! The ammo counter was removed on the feedback of a few testers who said it made the game significantly worse. This was before major balancing changes which would have made it good to re-implement. There's no recoil implemented for the same reason; I had a few people tell me that it made the game worse as it has to be casual enough to pick up and play very quickly without learning compensation patterns and whatnot in a jam. Melee becomes very necessary with the final boss though, although I get that due to the last minute balance changes which made the standard enemies significantly weaker, it becomes redundant.
The yellow bar on the right hand side is the "coolant bar". During development this would be spent by melee, sprinting and slow motion to make the player assess the situation and prioritize damage vs mobility, but this was cut at the request of testers, changed to be only spent by utilizing slow-motion, which runs out when the bar reaches zero.
The blue bar underneath health is the shields bar. This is a 100 damage buffer that regenerates quickly to allow the player to take a few hits before taking health damage, which can not be recovered. It's a way to avoid the player getting BS killed from behind; a volley of rounds from the AI will deplete this bar and only dent the health so long as the player reacts before they can let off another one, and the boss isn't too punishing so long as the player manages their shields well. It's an incentive to play smart and manage their regen without forcing them out of the fight to wait for health to regenerate since it goes very quickly; it's effectively now that the player is punished for taking multiple successive hits extremely rapidly, as it regenerates very fast and has no delay before it starts, so simply dodging out of the way of a hit is enough for it to recover significantly.
Slowing down time allows you to combine it with melee (the intended purpose). This lets you get off melee hits five times as fast relative to the world, so you can execute 5 melee combos on the boss during the stagger period, or take down a full crowd of enemies. It's all about synergizing it with other mechanics.
The dive roll originally innately lowered the accuracy of enemies shooting at the player, but this became incredibly abusable after the overheating mechanic was removed, so now it is just a quick method that is used to open the door for slow motion and cool feeling moments rather than impacting gameplay on its own in gunfights. However, it is still incredibly important to use against melee opponents such as the boss, where it is the only way to move fast enough in a given direction to avoid melee hits, which it is incredibly functional for. It is very difficult if not impossible to survive in combat against the final boss without extensive use of dodge rolling especially as it reaches the second phase, where you have to make split second reactions to the smoke particles to determine a direction and dodge roll away before her attacks land.
Thanks for the feedback. I'll definitely create a better guide on the HUD and look into ways to implement ammo limits without hurting the experience as testers decided it did. Unfortunately, I had to sacrifice most of the mechanical aspects that added depth and purpose to other mechanics and allowed for creative combinations of different movement and combat techniques together to make it a more casual, easy-going experience that anyone can pick up and have some fun with and not have to grapple with the hardcore elements that were present earlier in the game's life, as testers found that those mechanics added unnecessary complexity and difficulty and that removing them ultimately improved the game for them.