Jetpacks (#9023)

* Movement acceleration

* tweaks

* Weightless refactor coz fuck it

* CCVars

* weightless movement tweaks

* Some cleanup while I'm here

* dorkpacks

* thanks fork

* fixes

* zoomies

* toggles

* hmm

* yamls

* b

* so true

* Effects refactor

* namespace

* review

Content.Shared/Movement/Systems/SharedMoverController.Pushing.cs

@@ -0,0 +1,56 @@
+using Content.Shared.CCVar;
+using Content.Shared.Movement.Components;
+using Robust.Shared.Physics;
+using Robust.Shared.Physics.Dynamics;
+
+namespace Content.Shared.Movement.Systems;
+
+public abstract partial class SharedMoverController
+{
+    private bool _pushingEnabled;
+
+    private void InitializePushing()
+    {
+        _configManager.OnValueChanged(CCVars.MobPushing, SetPushing, true);
+    }
+
+    private void SetPushing(bool value)
+    {
+        if (_pushingEnabled == value) return;
+
+        _pushingEnabled = value;
+
+        if (_pushingEnabled)
+        {
+            _physics.KinematicControllerCollision += OnMobCollision;
+        }
+        else
+        {
+            _physics.KinematicControllerCollision -= OnMobCollision;
+        }
+    }
+
+    private void ShutdownPushing()
+    {
+        if (_pushingEnabled)
+            _physics.KinematicControllerCollision -= OnMobCollision;
+
+        _configManager.UnsubValueChanged(CCVars.MobPushing, SetPushing);
+    }
+
+    /// <summary>
+    ///     Fake pushing for player collisions.
+    /// </summary>
+    private void OnMobCollision(Fixture ourFixture, Fixture otherFixture, float frameTime, Vector2 worldNormal)
+    {
+        if (!_pushingEnabled) return;
+
+        var otherBody = otherFixture.Body;
+
+        if (otherBody.BodyType != BodyType.Dynamic || !otherFixture.Hard) return;
+
+        if (!EntityManager.TryGetComponent(ourFixture.Body.Owner, out IMobMoverComponent? mobMover) || worldNormal == Vector2.Zero) return;
+
+        otherBody.ApplyLinearImpulse(-worldNormal * mobMover.PushStrength * frameTime);
+    }
+}