Updated to work with MVC pattern, added comments

Assets/NinjaController.cs

@@ -0,0 +1,30 @@
+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+
+public class NinjaController : MonoBehaviour
+{
+    Ninja ninjaModel;
+    // Start is called before the first frame update
+    void Start()
+    {
+        ninjaModel = GetComponent<Ninja>();
+    }
+
+
+    void Update()
+    {
+        UpdateMovementInput();
+    }
+
+    void UpdateMovementInput()
+    {
+        ninjaModel.moveX = Input.GetAxis("Horizontal");
+
+        //If jump button, is pushed, execute jump function
+        if (Input.GetButtonDown("Jump"))
+        {
+            ninjaModel.Jump();
+        }
+    }
+}

Assets/NinjaView.cs

@@ -0,0 +1,38 @@
+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+
+public class NinjaView : MonoBehaviour
+{
+    Animator animator;
+    SpriteRenderer sprite;
+
+    // Start is called before the first frame update
+    void Start()
+    {
+        animator = GetComponent<Animator>();
+        sprite = GetComponent<SpriteRenderer>();
+    }
+
+
+    public void UpdateAnimator(float moveX, bool grounded)
+    {
+
+        //Based on the direction of MoveX, Flip the Sprite
+        //If the move is so tiny (e.g.) small move, then ignore flipping
+        float smallMove = 0.0001f;
+        if (moveX < -smallMove)
+        {
+            sprite.flipX = true;
+        }
+        else if (moveX > smallMove)
+        {
+            sprite.flipX = false;
+        }
+
+        // Animator parameters
+        //Sets the animation paramaters /position of the character based on its speed and groundedness
+        animator.SetFloat("speed", Mathf.Abs(moveX));
+        animator.SetBool("grounded", grounded);
+    }
+}

Assets/Scenes/SampleScene.unity

@@ -38,7 +38,7 @@ RenderSettings:
   m_ReflectionIntensity: 1
   m_CustomReflection: {fileID: 0}
   m_Sun: {fileID: 705507994}
-  m_IndirectSpecularColor: {r: 0.44657868, g: 0.4964124, b: 0.574817, a: 1}
+  m_IndirectSpecularColor: {r: 0.44657898, g: 0.4964133, b: 0.5748178, a: 1}
   m_UseRadianceAmbientProbe: 0
 --- !u!157 &3
 LightmapSettings:
@@ -310,6 +310,8 @@ GameObject:
   - component: {fileID: 1571386447}
   - component: {fileID: 1571386446}
   - component: {fileID: 1571386445}
+  - component: {fileID: 1571386448}
+  - component: {fileID: 1571386449}
   m_Layer: 0
   m_Name: Ninja
   m_TagString: Player
@@ -446,7 +448,7 @@ Rigidbody2D:
   m_Interpolate: 0
   m_SleepingMode: 1
   m_CollisionDetection: 0
-  m_Constraints: 0
+  m_Constraints: 4
 --- !u!114 &1571386447
 MonoBehaviour:
   m_ObjectHideFlags: 0
@@ -459,9 +461,35 @@ MonoBehaviour:
   m_Script: {fileID: 11500000, guid: de5ea80d1091547beaa63a3993619707, type: 3}
   m_Name: 
   m_EditorClassIdentifier: 
+  moveX: 0
+  grounded: 0
   speed: 10
   jumpspeed: 20
   maxJumpTime: 0.2
+--- !u!114 &1571386448
+MonoBehaviour:
+  m_ObjectHideFlags: 0
+  m_CorrespondingSourceObject: {fileID: 0}
+  m_PrefabInstance: {fileID: 0}
+  m_PrefabAsset: {fileID: 0}
+  m_GameObject: {fileID: 1571386441}
+  m_Enabled: 1
+  m_EditorHideFlags: 0
+  m_Script: {fileID: 11500000, guid: da252e95c040c9e4c8061061074031d6, type: 3}
+  m_Name: 
+  m_EditorClassIdentifier: 
+--- !u!114 &1571386449
+MonoBehaviour:
+  m_ObjectHideFlags: 0
+  m_CorrespondingSourceObject: {fileID: 0}
+  m_PrefabInstance: {fileID: 0}
+  m_PrefabAsset: {fileID: 0}
+  m_GameObject: {fileID: 1571386441}
+  m_Enabled: 1
+  m_EditorHideFlags: 0
+  m_Script: {fileID: 11500000, guid: 3f90f732f2d4c6e41b1064dffd28b0ef, type: 3}
+  m_Name: 
+  m_EditorClassIdentifier: 
 --- !u!1 &1842770162
 GameObject:
   m_ObjectHideFlags: 0
@@ -586,8 +614,8 @@ Transform:
   m_PrefabAsset: {fileID: 0}
   m_GameObject: {fileID: 1842770162}
   m_LocalRotation: {x: 0, y: 0, z: 0, w: 1}
-  m_LocalPosition: {x: 0.39, y: -3.17, z: 0}
-  m_LocalScale: {x: 2, y: 1, z: 1}
+  m_LocalPosition: {x: -0.01, y: -3.17, z: 0}
+  m_LocalScale: {x: 3.7220402, y: 1, z: 1}
   m_Children: []
   m_Father: {fileID: 0}
   m_RootOrder: 3

Assets/Script/Ninja.cs

@@ -4,8 +4,8 @@
 
 public class Ninja : MonoBehaviour
 {
-    float moveX;
-    bool grounded;
+    [HideInInspector] public float moveX;
+    [HideInInspector] public bool grounded;
     bool jumping;
 
     float jumpTime;
@@ -15,74 +15,66 @@ public class Ninja : MonoBehaviour
     public float jumpspeed = 1.0f;
     public float maxJumpTime = 1.0f;
 
-    Animator animator;
     Rigidbody2D rb;
     BoxCollider2D boxCollider;
-    SpriteRenderer sprite;
+    NinjaView ninjaView;
 
     void Start()
     {
-        animator = GetComponent<Animator>();
+        ninjaView = GetComponent<NinjaView>();
         rb = GetComponent<Rigidbody2D>();
         boxCollider = GetComponent<BoxCollider2D>();
-        sprite = GetComponent<SpriteRenderer>();
+
     }
 
     // Update is called once per frame
     void Update()
     {
-        // Is platform below us?
-        float selfHeightOffset = (boxCollider.size.y / 2.0f) + 0.1f;
-        float rayLen =  0.05f;
-        Vector2 pos2D = (Vector2)transform.position;
-       // Debug.DrawRay(pos2D - (Vector2.up * selfHeightOffset), -Vector2.up * rayLen, Color.red);
-        RaycastHit2D hit = Physics2D.Raycast(pos2D - (Vector2.up * selfHeightOffset), -Vector2.up, rayLen);
-
-        grounded = false;
-        if (hit.collider != null)
-        {
-            if (hit.collider.CompareTag("Platform"))
-            {
-                grounded = true;
-            }
-        }
+        DetectGround();
 
-        // Jumping
+        // Jumping 
         if (grounded)
         {
-            moveX = Input.GetAxis("Horizontal");
-
 
             if (jumpTime < 0.0f)
             {
                 jumping = false;
             }
         }
+        jumpTime -= Time.deltaTime;
 
+        //Updates the animator based on current movement.
+        ninjaView.UpdateAnimator(moveX, grounded);
 
-        bool jumpPressed = Input.GetButtonDown("Jump");
-        if (grounded && jumpPressed && !jumping)
-        {
-            jumping = true;
-            jumpTime = maxJumpTime;
-        }
+    }
 
-        jumpTime -= Time.deltaTime;
+    void DetectGround()
+    {
+        // Is platform below us? Get raycast based on position directly below height of the player's box collider
+        float selfHeightOffset = (boxCollider.size.y / 2.0f) + 0.1f;
+        float rayLen = 0.05f;
+        Vector2 pos2D = (Vector2)transform.position;
+        // Debug.DrawRay(pos2D - (Vector2.up * selfHeightOffset), -Vector2.up * rayLen, Color.red);
+        RaycastHit2D hit = Physics2D.Raycast(pos2D - (Vector2.up * selfHeightOffset), -Vector2.up, rayLen);
 
-        // Reverse horizontal 
-        float smallMove = 0.0001f;
-        if (moveX < -smallMove)
-        {
-            sprite.flipX = true;
-        }
-        else if (moveX > smallMove)
+        grounded = false;
+        //If the raycast is touching the platform, then character is grounded and stop gravity from occuring.
+        if (hit.collider != null)
         {
-            sprite.flipX = false;
-        }
+            if (hit.collider.CompareTag("Platform"))
+            {
+                grounded = true;
+            }
+        }
+    }
 
-        // Animator parameters
-        animator.SetFloat("speed", Mathf.Abs(moveX));
-        animator.SetBool("grounded", grounded);
+    public void Jump()
+    {
+        if (grounded && !jumping)
+        {
+            jumping = true;
+            jumpTime = maxJumpTime;
+        }
     }
 
     // Physic stuff