add negating conditions page

content/negating-conditions.md

@@ -1 +1,35 @@
-TBD
+To invert the condition and produce a truthy result when the conditions is not met, use the `not` operator. This operator negates the condition that follows it.
+
+```sb
+if
+    not is_player_playing 0
+then
+    // execute this code if the player is not playing
+end
+```
+
+`not` can be used with math expressions as well:
+
+```sb
+if not x > 5 // if x is not greater than 5
+then
+    //
+end
+```
+
+Some operators have a negated version, i.e. an operator that does the opposite. For example, `==` is the equality operator, and `<>` is the inequality operator. The following two conditions are equivalent:
+
+```sb
+not x == 5
+x <> 5
+```
+
+Here is a list of negated operators:
+
+| Operator | Negated operator |
+| -------- | ---------------- |
+| `==`     | `<>`             |
+| `>`      | `<=`             |
+| `<`      | `>=`             |
+| `>=`     | `<`              |
+| `<=`     | `>`              |