From 5b1d0ca04946a1bb42144c2f7da771227822383e Mon Sep 17 00:00:00 2001
From: minjaesong <alswo9628@gmail.com>
Date: Sun, 8 Feb 2026 03:53:10 +0900
Subject: [PATCH] platform surface friction

---
 .../torvald/terrarum/gameactors/ActorMovingPlatform.kt   | 7 ++++++-
 src/net/torvald/terrarum/gameactors/ActorWithBody.kt     | 9 +++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/net/torvald/terrarum/gameactors/ActorMovingPlatform.kt b/src/net/torvald/terrarum/gameactors/ActorMovingPlatform.kt
index 120c5a27b..496e24e92 100644
--- a/src/net/torvald/terrarum/gameactors/ActorMovingPlatform.kt
+++ b/src/net/torvald/terrarum/gameactors/ActorMovingPlatform.kt
@@ -7,6 +7,8 @@ import com.badlogic.gdx.graphics.g2d.SpriteBatch
 import com.badlogic.gdx.graphics.g2d.TextureRegion
 import net.torvald.terrarum.INGAME
 import net.torvald.terrarum.TerrarumAppConfiguration.TILE_SIZE
+import net.torvald.terrarum.blockproperties.Block
+import net.torvald.terrarum.gameitems.ItemID
 import net.torvald.terrarum.modulebasegame.gameactors.ActorHumanoid
 import org.dyn4j.geometry.Vector2
 
@@ -21,7 +23,7 @@ import org.dyn4j.geometry.Vector2
  */
 open class ActorMovingPlatform() : ActorWithBody() {
 
-    protected var tilewiseWidth = 3
+    protected var tilewiseWidth = 3 // default fallback value when no args were given
 
     constructor(newTilewiseWidth: Int) : this() {
         this.tilewiseWidth = newTilewiseWidth
@@ -50,6 +52,9 @@ open class ActorMovingPlatform() : ActorWithBody() {
     /** Minimum combined Y velocity to count as "jumping up" (prevents mount while jumping). */
     @Transient private val JUMP_THRESHOLD_Y = -0.5
 
+    /** Block whose friction this platform impersonates. Riders use this for feet friction. */
+    var surfaceBlock: ItemID = Block.STONE
+
     @Transient private var platformTexture: Texture? = null
     @Transient private var platformTextureRegion: TextureRegion? = null
 
diff --git a/src/net/torvald/terrarum/gameactors/ActorWithBody.kt b/src/net/torvald/terrarum/gameactors/ActorWithBody.kt
index ef2e841c7..03447a814 100644
--- a/src/net/torvald/terrarum/gameactors/ActorWithBody.kt
+++ b/src/net/torvald/terrarum/gameactors/ActorWithBody.kt
@@ -294,6 +294,7 @@ open class ActorWithBody : Actor {
     private inline val grounded: Boolean
         get() = if (world == null) true else {
             isNoClip ||
+            platformsRiding.isNotEmpty() ||
             (world!!.gravitation.y > 0 && isWalled(hitbox, COLLIDING_BOTTOM) ||
              world!!.gravitation.y < 0 && isWalled(hitbox, COLLIDING_TOP))
         }
@@ -1692,6 +1693,14 @@ open class ActorWithBody : Actor {
     // after all, feet friction is what it matters
     internal inline val feetFriction: Double
         get() {
+            // When riding a platform, use the platform's surface block friction
+            if (platformsRiding.isNotEmpty()) {
+                val platform = INGAME.getActorByID(platformsRiding[0])
+                if (platform is ActorMovingPlatform) {
+                    return getTileFriction(platform.surfaceBlock)
+                }
+            }
+
             var friction = 0.0
             forEachFeetTileNum {
                 // get max friction