DOCUMENTATION: Document coding contract's generation and rewards (#2624)

src/Documentation/doc/en/basic/codingcontracts.md

@@ -6,11 +6,29 @@ Coding Contracts are files with the `.cct` extension.
 They can be accessed through the [Terminal](terminal.md) or through [Scripts](scripts.md) using the [Coding Contract API](../../../../../markdown/bitburner.codingcontract.md).
 
 Each contract has a limited number of attempts.
-If you provide the wrong answer too many times and exceed the number of attempts, the contract will self destruct (delete itself).
+If you provide the wrong answer too many times and exceed the number of attempts, the contract will self-destruct (delete itself).
 
 Coding Contracts are randomly generated and spawn over time. Initially, you'll only see a small range of the easier contracts, but as you progress further through the game more challenging ones will unlock.
 They can appear on any [server](servers.md) (including your home computer), except for your purchased [servers](servers.md).
 
+## Contract generation
+
+### Online
+
+Every 10 minutes, the game makes three independent attempts to generate a contract on normal servers, each with a base
+25% chance. This probability decreases based on the total number of contracts across all servers. In most cases, you can
+assume a ~25% success rate per attempt.
+
+### Offline
+
+When the game is launched after being offline, the offline time is used to calculate the number of generation attempts.
+The same rules and probabilities from the online generation process apply.
+
+### Dark Net
+
+Opening cache files on [darknet](../programming/darknet.md) servers also has a chance to generate a contract, but with
+lower rewards. Contracts generated this way grant 50% lower rewards than those generated randomly on normal servers.
+
 ## Running in Terminal
 
 To run a Coding Contract in the [Terminal](terminal.md), simply use the `run` command:
@@ -136,7 +154,18 @@ There are currently four possible rewards for solving a Coding Contract:
 - [Company](companies.md) [Reputation](reputation.md) for a specific [Company](companies.md)
 - Money
 
-The `amount` of the reward varies based on the difficulty of the problem posed by the Coding Contract.
+The reward type is randomly chosen at spawn time. If the chosen reward is invalid upon completion (e.g., requirements
+are not met), it falls back to an alternative type:
+
+- Specific faction reputation ⇒ Money
+- All factions' reputation ⇒ Money
+- Company reputation ⇒ Specific faction reputation or all factions' reputation (50% chance for each).
+  If the fallback reward is also invalid, the reward defaults to Money.
+
+For example, if a contract is set to reward "All Factions' Reputation" but you have not joined any factions at the time
+of submission, you will receive Money instead.
+
+The amount of the reward varies based on the difficulty of the problem posed by the Coding Contract.
 
 ## Notes