Changed run/walk to be based more off of momentum. Fixed jump bug.

objects/scenes/demo/demo.tscn

@@ -162,9 +162,11 @@ position = Vector2(755, 0)
 position = Vector2(1, 0)
 safe_margin = 0.16
 script = ExtResource("2_oekxy")
-FloatingWalkSpeed = 3.5
-WalkSpeed = 4.0
+FloatingWalkAcceleration = 30.0
+WalkAcceleration = 80.0
 JumpHeight = 6.0
+DragArea = 1.525
+AirDensity = 1.3
 DebugTextLabel = NodePath("Label")
 Sprite = NodePath("AnimatedSprite2D")
 Mass = 0.5
@@ -183,7 +185,6 @@ animation = &"walk"
 zoom = Vector2(3, 3)
 
 [node name="Label" type="Label" parent="Player/CharacterBody2D" unique_id=436935745]
-visible = false
 offset_left = 22.0
 offset_top = -75.0
 offset_right = 139.0

src/components/PlayerPhysicsController.cs

@@ -4,17 +4,26 @@ using System.Diagnostics;
 
 public partial class PlayerPhysicsController : CharacterBody2D {
     [Export]
-    public float FloatingWalkSpeed { get; set; } = 1f;
+    public float FloatingWalkAcceleration { get; set; } = 1f;
     [Export]
     public float RunMultiplier { get; set; } = 1.84f;
     [Export]
-    public float WalkSpeed { get; set; } = 3f;
+    public float WalkAcceleration { get; set; } = 3f;
 
     [Export]
     public float JumpHeight { get; set; } = 5.5f;
 
     private float PeakTime { get; set; } = 0.1f;
 
+    [Export]
+    public float DragArea { get; set; } = 4f;
+
+    [Export]
+    public float AirDensity { get; set; } = 37.26982f;
+
+    [Export]
+    public float DragCoefficient { get; set; } = 1.3f;
+
     [Export]
     public Label DebugTextLabel { get; set; }
 
@@ -22,7 +31,9 @@ public partial class PlayerPhysicsController : CharacterBody2D {
     public AnimatedSprite2D Sprite { get; set; }
 
     [Export]
-    public float Gravity { get; set; } = 30f;
+    public float Gravity { get; set; } = 30.625f;
+
+    private float TilesToMeters => 9.81f / Gravity;
 
     [Export]
     public float UnitToPx { get; set; } = 32;
@@ -38,6 +49,19 @@ public partial class PlayerPhysicsController : CharacterBody2D {
         _lv = Mathf.Sqrt(Mathf.Pow(Gravity * PeakTime / 2, 2) + 2 * Gravity * JumpHeight);
     }
 
+    private float CalculateRunDrag(float delta) {
+        return 
+            0.5f * 
+            DragCoefficient * 
+            (Mathf.Pow(TilesToMeters, 3) * AirDensity) * 
+            (Mathf.Pow(TilesToMeters, 2) * DragArea) * 
+            Mathf.Pow(Velocity.X * TilesToMeters, 2) * 
+            _invmass * 
+            -Mathf.Sign(Velocity.X) *
+            delta *
+            (1f / TilesToMeters);
+    }
+
     public override void _Ready() {
         RecalculateLv();
         base._Ready();
@@ -74,9 +98,12 @@ public partial class PlayerPhysicsController : CharacterBody2D {
         var lastCollision = this.IsOnCeiling();
         RecalculateLv();
 
-        float velx = 0f;
+        float maxOpposingVel = -(Velocity.X * 0.99f / UnitToPx);
+        float velx = (Velocity.X / UnitToPx) + Mathf.Clamp(CalculateRunDrag((float)delta), Math.Min(maxOpposingVel, -maxOpposingVel), Math.Max(maxOpposingVel, -maxOpposingVel));
         float vely = (Velocity.Y / UnitToPx) + Gravity * (float)delta;
 
+        if (Mathf.Abs(velx) < 0.5) velx = 0;
+
         var grounded = this.IsOnFloor();
         var coyoteGrounded = _timeOffGround < CoyoteTiming;
         if (grounded || coyoteGrounded) {
@@ -87,10 +114,14 @@ public partial class PlayerPhysicsController : CharacterBody2D {
                 vely = -_lv;
             }
 
+            if (!grounded && coyoteGrounded && Input.IsActionJustReleased("jump") && vely < 0) {
+                vely *= 1/4f;
+            }
+
             if (Input.IsActionPressed("run")) {
-                velx = WalkSpeed * RunMultiplier;
+                velx += xAxis * WalkAcceleration * (float)delta * RunMultiplier;
             } else {
-                velx = WalkSpeed;
+                velx += xAxis * WalkAcceleration * (float)delta;
             }
         } else {
             if (Input.IsActionJustReleased("jump") && vely < 0) {
@@ -98,20 +129,18 @@ public partial class PlayerPhysicsController : CharacterBody2D {
             }
 
             if (Input.IsActionPressed("run")) {
-                velx = FloatingWalkSpeed * RunMultiplier;
+                velx += xAxis * FloatingWalkAcceleration * (float)delta * RunMultiplier;
             } else {
-                velx = FloatingWalkSpeed;
+                velx += xAxis * FloatingWalkAcceleration * (float)delta; 
             }
         }
 
-        velx *= xAxis;
-
         DebugTextLabel.Text = 
             $"grounded: {grounded}\n" + 
             $"vely: {vely}\n" +
             $"velx: {velx}\n" +
             $"lv  : {_lv:F2} or {_lv/(float)delta:F2}\n" +
-            $"tg  : {_timeOffGround}";
+            $"rd  : {CalculateRunDrag((float)delta)}";
         // Force = new Vector2(0, forcey);
         Velocity = new Vector2(velx, vely) * UnitToPx;