Horror...here's some screenies from the current battle system...
On the upper left corner you can probably see the "red dude", which actually represents the level of damage that you have received. When the figure is completely red, you're dead. There is no way to cure yourself during the battle, since the only curing items in the game are the first aid kits (which only cure one level of damage). Neither can you access the inventory in the middle of the fight (have you ever seen anyone starting to calmly investigate his backpack in the middle of a combat situation?

), so keep your pistol equipped when you think there's gonna be a fight ahead.
Right next to it there are the icons representing the Fist-fight, Shoot, and Escape actions, and their hotkeys (so, to change between the melee & pistol, you just have use the number keys, while fighting with the right hand and the mouse).
The green bar is the hit gauge. For example, when using the pistol, you will have to move the mouse in horizontal line to select between the enemies. Then, when you've got one in the crosshair, just hold down the left-mouse button, and lift your finger when the gauge bar is full. Of course, you can shoot with the speed of light if you wish, but you probably won't hit the enemies, as the shots more or less start hitting when the gauge is midway full (depending on the enemy, if its an elephant, don't worry...).
At the moment it's quite easy to shoot down the enemies, but it gets a bit more difficult when there's 3 of them. Anyways, I'm not planning to give the pistol in the beginning of the game.