diff --git a/as4/README.md b/as4/README.md
index e47914f..0ac1e67 100644
--- a/as4/README.md
+++ b/as4/README.md
@@ -9,11 +9,11 @@ cd cs381
 git submodule update --init --recursive
 ```
 
-Navigate to the `as3` directory, create a build directory, and run CMake to
+Navigate to the `as4` directory, create a build directory, and run CMake to
 generate the build files:
 
 ```sh
-cd as3
+cd as4
 mkdir -p build
 cd build
 cmake ..
@@ -25,34 +25,47 @@ Compile the code using `make`:
 make
 ```
 
-This should create an executable named `as3` in the `build` directory. You can
+This should create an executable named `as4` in the `build` directory. You can
 run the executable with the following command:
 
 ```sh
-./as3
+./as4
 ```
 
 # Instructions on how to use the program
 
-Hold W and S to accelerate the penguin forward and backward. Use A and D to
-change heading direction. This allows you to steer the penguin around the
+Hold W and S to accelerate the selected entity forward and backward. Use A and
+D to change heading direction. This allows you to steer the entity around the
 environment.
 
-Use the arrow keys to change the camera's rotation (pitch and yaw) with respect
-to the penguin, allowing you to look around while the penguin moves.
+Use TAB to switch between entities. The currently selected entity will
+be drawn with a bounding box.
+
+When the eagle is selected, press Q and Z to change the pitch.
 
 # Readme Question
 
-`dt` is delta time, which is the time elapsed between each frame, which can be
-found by taking the current time and subtracting the time from the previous
-frame. Raylib provides a function `GetFrameTime()` that returns the time
-elapsed since the last frame, which can be used to calculate `dt`. By using
-`dt`, it ensures that physics calculations are independent of frame rate, since
-otherwise the velocity would be in terms of units per frame rather than units
-per second. By multiplying the velocity by `dt`, it converts the velocity to
-units per second, allowing for consistent movement regardless of the frame
-rate.
+The entity selection system works by when TAB is pressed (key down only on one
+frame), the program increments the index of the currently selected entity.
+Selection wraps around to the first entity when it exceeds the number of
+entities in the game. Movement keys only apply to the selected entity, which is
+determined by the selected index. When drawing, the selected index is compared
+to the index of each entity, and if they match, a bounding box is drawn around
+the entity to indicate that it is selected.
+
+Both monolithic and ad-hoc approaches to entity management are fast to setup
+since they require the least amount of code/boilerplate to get something
+working. However, monolithic entities are easier to scale, since in ad-hoc, you
+have to write the entire state and behavior of the entity (its variables,
+methods, etc) for each entity that exists. Ad-hoc is faster to work with only
+when managing few entities with very different behavior.
+
+For this particular assignment, the monolithic approach is more suitable since
+most of the entities share similar behavior (change velocity) and state
+(position, speed, heading). This however still became more difficult to manage
+when adding the eagle that had an additional pitch variable and flying
+behavior.
 
 # Extra Credit
 
-The camera moves with the penguin and can be rotated around the penguin using the arrow keys.
+The eagle can move in 3D space with an additional DOF compared to the penguins.