learning env example docs for 2v1

docs/Learning-Environment-Examples.md

 * Goal:
   * Get the ball into the opponent's goal while preventing
   the ball from entering own goal.
-  * Goalie:
-  Behavior Parameters : Soccer.
+  Behavior Parameters : SoccerTwos.
 * Agent Reward Function (dependent):
     * +1 When ball enters opponent's goal.
     * -1 When ball enters team's goal.
     and 3 ray-casts backward distributed over 90 degrees each detecting 6 possible object types, along with the object's distance.
-    The forward ray-casts contribute 264 state dimensions and backward 72 state dimensions.
+    The forward ray-casts contribute 264 state dimensions and backward 72 state dimensions over three observation stacks.
   * Vector Action space: (Discrete) Three branched actions corresponding to forward, backward, sideways movement,
       as well as rotation.
   * Visual Observations: None
     * Default: 9.81
     * Recommended minimum: 6
     * Recommended maximum: 20
+
+# Strikers Vs. Goalie
+
+![StrikersVsGoalie](images/strikersvsgoalie.png)
+
+* Set-up: Environment where two agents compete in a 2 vs 1 soccer variant.
+* Goal:
+  * Striker: Get the ball into the opponent's goal.
+  * Goalie: Keep the ball out of the goal.
+* Agents: The environment contains three agents. Two Strikers and one Goalie.
+  Behavior Parameters : Striker, Goalie.
+* Striker Agent Reward Function (dependent):
+    * +1 When ball enters opponent's goal.
+    * -0.001 Existential penalty.
+* Goalie Agent Reward Function (dependent):
+    * -1 When ball enters goal.
+    * 0.001 Existential bonus.
+* Behavior Parameters:
+  * Striker is the same as SoccerTwos above.
+  * Goalie Vector Observation space: 984 corresponding to 41 ray-casts distributed over 360 degrees
+    each detecting 6 possible object types, along with the object's distance and 3 observation stacks.
+  * Goalie Vector Action space: (Discrete) Three branched actions corresponding to forward, backward, sideways movement,
+      as well as rotation.
+  * Visual Observations: None
+* Float Properties: Two
+  * ball_scale: Specifies the scale of the ball in the 3 dimensions (equal across the three dimensions)
+    * Default: 7.5
+    * Recommended minimum: 4
+    * Recommended maximum: 10
+  * gravity: Magnitude of the gravity
+    * Default: 9.81
+    * Recommended minimum: 6
+    * Recommended maximum: 20
+
 
 ## Walker