Critical chance system

Hello, i try make some critical chance system :

Code (CSharp):

1.     float randValue = Random.value;
2.     if (randValue < .90f) // 90% of the time
3.     {
4.         // Do Normal Attack
5.     }
6.    
7.     else // 10% of the time
8.     {
9.         // Do Normal Attack x 2
10.     }
11.  

Actually my Critical Chance are 10% , But I don't know how to increase Critical Chance.
For example, if i do a skill system, how could I raise 5% (so 15% total) my critical chance ? I don t know how to change variable, how creta logic system...

I guess it is simple for some of you, but i'm really noob...

Thank's for any help

 

Code (csharp):

1.  
2. float target = 0.1f; // replace value with chance calculation
3. float randValue = Random.value;
4.  
5. if (randValue < (1f-target))
6. {...
7.  
8.  

 

Something like this would work:

Code (CSharp):

1. float critChance = 0.0f;
2.  
3. void IncreaseCritChance(float critInc)
4. {
5.      critChance += critInc;
6.  
7.      //Never let the crit chance go out of range
8.      if(critChance > 100.0f)
9.      {
10.           critChance = 100.0f;
11.      }
12. }
13.  
14. void DoAttack()
15. {
16.      float randValue = Random.value;
17.      if(randValue < critChance)
18.      {
19.           //Do crit attack
20.      }
21.      else
22.      {
23.           //Do normal attach
24.      }
25. }

This is obviously sudo code, but you can get the gist

 

Okay ! Many Thank's for quick answer, very helpfull