diff --git a/modules/io.github.xenfork.freeworld.client/src/main/java/io/github/xenfork/freeworld/client/Freeworld.java b/modules/io.github.xenfork.freeworld.client/src/main/java/io/github/xenfork/freeworld/client/Freeworld.java
index a81dbe0..b8c3fb0 100644
--- a/modules/io.github.xenfork.freeworld.client/src/main/java/io/github/xenfork/freeworld/client/Freeworld.java
+++ b/modules/io.github.xenfork.freeworld.client/src/main/java/io/github/xenfork/freeworld/client/Freeworld.java
@@ -23,6 +23,7 @@
 import io.github.xenfork.freeworld.world.block.BlockTypes;
 import io.github.xenfork.freeworld.world.entity.Entity;
 import io.github.xenfork.freeworld.world.entity.EntityTypes;
+import io.github.xenfork.freeworld.world.entity.component.OnGroundComponent;
 import org.joml.Vector2d;
 import org.slf4j.Logger;
 import overrun.marshal.Unmarshal;
@@ -176,18 +177,19 @@ private void onCursorPos(double x, double y) {
 
     private void tick() {
         camera.preUpdate();
-        final double speed = glfw.getKey(window, GLFW.KEY_LEFT_CONTROL) == GLFW.PRESS ? 1.0 : 0.5;
+        final boolean onGround = player.hasComponent(OnGroundComponent.ID);
+        double speed = onGround ? 0.1 : 0.07;
+        if (glfw.getKey(window, GLFW.KEY_LEFT_CONTROL) == GLFW.PRESS) speed *= 2.0;
         double xo = 0.0;
-        double yo = 0.0;
         double zo = 0.0;
         if (glfw.getKey(window, GLFW.KEY_W) == GLFW.PRESS) zo -= 1.0;
         if (glfw.getKey(window, GLFW.KEY_S) == GLFW.PRESS) zo += 1.0;
         if (glfw.getKey(window, GLFW.KEY_A) == GLFW.PRESS) xo -= 1.0;
         if (glfw.getKey(window, GLFW.KEY_D) == GLFW.PRESS) xo += 1.0;
-        if (glfw.getKey(window, GLFW.KEY_LEFT_SHIFT) == GLFW.PRESS) yo -= 1.0;
-        if (glfw.getKey(window, GLFW.KEY_SPACE) == GLFW.PRESS) yo += 1.0;
-        player.acceleration().value().set(xo, yo, zo).mul(speed);
-        player.velocity().value().zero();
+        if (onGround && glfw.getKey(window, GLFW.KEY_SPACE) == GLFW.PRESS) {
+            player.velocity().value().y = 0.5;
+        }
+        player.acceleration().value().set(xo, 0.0, zo).mul(speed);
         world.tick();
 
         if (blockDestroyTimer >= 2) {
diff --git a/modules/io.github.xenfork.freeworld.core/src/main/java/io/github/xenfork/freeworld/world/entity/Entity.java b/modules/io.github.xenfork.freeworld.core/src/main/java/io/github/xenfork/freeworld/world/entity/Entity.java
index d9eec03..27b2aeb 100644
--- a/modules/io.github.xenfork.freeworld.core/src/main/java/io/github/xenfork/freeworld/world/entity/Entity.java
+++ b/modules/io.github.xenfork.freeworld.core/src/main/java/io/github/xenfork/freeworld/world/entity/Entity.java
@@ -51,6 +51,10 @@ public void setComponent(EntityComponent component) {
         componentMap.put(component.componentId(), component);
     }
 
+    public void removeComponent(Identifier id) {
+        componentMap.remove(id);
+    }
+
     @SuppressWarnings("unchecked")
     public <T extends EntityComponent> T getComponent(Identifier id) {
         return (T) componentMap.get(id);
diff --git a/modules/io.github.xenfork.freeworld.core/src/main/java/io/github/xenfork/freeworld/world/entity/component/EntityComponent.java b/modules/io.github.xenfork.freeworld.core/src/main/java/io/github/xenfork/freeworld/world/entity/component/EntityComponent.java
index 0593276..89deb78 100644
--- a/modules/io.github.xenfork.freeworld.core/src/main/java/io/github/xenfork/freeworld/world/entity/component/EntityComponent.java
+++ b/modules/io.github.xenfork.freeworld.core/src/main/java/io/github/xenfork/freeworld/world/entity/component/EntityComponent.java
@@ -16,7 +16,14 @@
  * @author squid233
  * @since 0.1.0
  */
-public sealed interface EntityComponent permits BoundingBoxComponent, AccelerationComponent, EyeHeightComponent, PositionComponent, RotationXYComponent, VelocityComponent {
+public sealed interface EntityComponent permits
+    AccelerationComponent,
+    BoundingBoxComponent,
+    EyeHeightComponent,
+    OnGroundComponent,
+    PositionComponent,
+    RotationXYComponent,
+    VelocityComponent {
     /**
      * {@return a unique identifier of this component}
      */
diff --git a/modules/io.github.xenfork.freeworld.core/src/main/java/io/github/xenfork/freeworld/world/entity/component/OnGroundComponent.java b/modules/io.github.xenfork.freeworld.core/src/main/java/io/github/xenfork/freeworld/world/entity/component/OnGroundComponent.java
new file mode 100644
index 0000000..5d90247
--- /dev/null
+++ b/modules/io.github.xenfork.freeworld.core/src/main/java/io/github/xenfork/freeworld/world/entity/component/OnGroundComponent.java
@@ -0,0 +1,27 @@
+/*
+ * freeworld - 3D sandbox game
+ * Copyright (C) 2024  XenFork Union
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ */
+
+package io.github.xenfork.freeworld.world.entity.component;
+
+import io.github.xenfork.freeworld.core.Identifier;
+
+/**
+ * @author squid233
+ * @since 0.1.0
+ */
+public final class OnGroundComponent implements EntityComponent {
+    public static final Identifier ID = Identifier.ofBuiltin("on_ground");
+    public static final OnGroundComponent INSTANCE = new OnGroundComponent();
+
+    @Override
+    public Identifier componentId() {
+        return ID;
+    }
+}
diff --git a/modules/io.github.xenfork.freeworld.core/src/main/java/io/github/xenfork/freeworld/world/entity/system/MotionSystem.java b/modules/io.github.xenfork.freeworld.core/src/main/java/io/github/xenfork/freeworld/world/entity/system/MotionSystem.java
index dd72a5a..f6d5be3 100644
--- a/modules/io.github.xenfork.freeworld.core/src/main/java/io/github/xenfork/freeworld/world/entity/system/MotionSystem.java
+++ b/modules/io.github.xenfork.freeworld.core/src/main/java/io/github/xenfork/freeworld/world/entity/system/MotionSystem.java
@@ -45,7 +45,7 @@ public void process(World world, List<Entity> entities) {
                 velocity.add(acceleration);
                 MathUtil.moveRelative(velocity.x(), velocity.y(), velocity.z(), rotation.y(), movement);
 
-                AABBox boundingBox = null;
+                AABBox boundingBox;
                 if (entity.hasComponent(BoundingBoxComponent.ID)) {
                     boundingBox = entity.boundingBox().value();
 
@@ -73,9 +73,16 @@ public void process(World world, List<Entity> entities) {
                         }
                     }
 
+                    final double originMovementY = movement.y();
                     for (AABBox box : boxes) {
                         movement.y = box.clipYCollide(boundingBox, movement.y());
                     }
+                    if (originMovementY != movement.y && originMovementY < 0.0) {
+                        velocity.y = 0.0;
+                        entity.addComponent(OnGroundComponent.INSTANCE);
+                    } else {
+                        entity.removeComponent(OnGroundComponent.ID);
+                    }
                     position.y += movement.y();
                     boundingBox = computeBox(boundingBox, position);
 
@@ -95,7 +102,8 @@ public void process(World world, List<Entity> entities) {
                     position.add(movement);
                 }
 
-                velocity.mul(0.5);
+                velocity.y -= 0.08;
+                velocity.mul(0.8, 0.98, 0.8);
             }
         }
     }