Reduce knocked down players tile friction (#11035)

Content.Shared/Stunnable/SharedStunSystem.cs

@@ -26,6 +26,12 @@ namespace Content.Shared.Stunnable
         [Dependency] private readonly StatusEffectsSystem _statusEffectSystem = default!;
         [Dependency] private readonly MovementSpeedModifierSystem _movementSpeedModifierSystem = default!;
 
+        /// <summary>
+        /// Friction modifier for knocked down players.
+        /// Doesn't make them faster but makes them slow down... slower.
+        /// </summary>
+        public const float KnockDownModifier = 0.4f;
+
         public override void Initialize()
         {
             SubscribeLocalEvent<KnockedDownComponent, ComponentInit>(OnKnockInit);
@@ -48,6 +54,8 @@ namespace Content.Shared.Stunnable
             SubscribeLocalEvent<KnockedDownComponent, InteractHandEvent>(OnInteractHand);
             SubscribeLocalEvent<SlowedDownComponent, RefreshMovementSpeedModifiersEvent>(OnRefreshMovespeed);
 
+            SubscribeLocalEvent<KnockedDownComponent, TileFrictionEvent>(OnKnockedTileFriction);
+
             // Attempt event subscriptions.
             SubscribeLocalEvent<StunnedComponent, UpdateCanMoveEvent>(OnMoveAttempt);
             SubscribeLocalEvent<StunnedComponent, InteractionAttemptEvent>(OnInteractAttempt);
@@ -205,6 +213,7 @@ namespace Content.Shared.Stunnable
             if (args.Handled || knocked.HelpTimer > 0f)
                 return;
 
+            // TODO: This should be an event.
             if (HasComp<SleepingComponent>(uid))
                 return;
 
@@ -215,11 +224,16 @@ namespace Content.Shared.Stunnable
 
             SoundSystem.Play(knocked.StunAttemptSound.GetSound(), Filter.Pvs(uid), uid, AudioHelpers.WithVariation(0.05f));
 
-            knocked.Dirty();
+            Dirty(knocked);
 
             args.Handled = true;
         }
 
+        private void OnKnockedTileFriction(EntityUid uid, KnockedDownComponent component, ref TileFrictionEvent args)
+        {
+            args.Modifier *= KnockDownModifier;
+        }
+
         #region Attempt Event Handling
 
         private void OnMoveAttempt(EntityUid uid, StunnedComponent stunned, UpdateCanMoveEvent args)