diff --git a/StackLayoutManager/src/main/java/com/littlemango/stacklayoutmanager/DefaultAnimation.kt b/StackLayoutManager/src/main/java/com/littlemango/stacklayoutmanager/DefaultAnimation.kt
index 9742e9e..d8b0b81 100644
--- a/StackLayoutManager/src/main/java/com/littlemango/stacklayoutmanager/DefaultAnimation.kt
+++ b/StackLayoutManager/src/main/java/com/littlemango/stacklayoutmanager/DefaultAnimation.kt
@@ -2,6 +2,7 @@ package com.littlemango.stacklayoutmanager
 
 import android.view.View
 import com.littlemango.stacklayoutmanager.StackLayoutManager.ScrollOrientation
+import kotlin.math.pow
 
 class DefaultAnimation(scrollOrientation: ScrollOrientation, visibleCount: Int) : StackAnimation(scrollOrientation, visibleCount) {
 
@@ -72,8 +73,8 @@ class DefaultAnimation(scrollOrientation: ScrollOrientation, visibleCount: Int)
             scale = 1 - ((1 - mOutScale) * firstMovePercent)
             rotation = mOutRotation * firstMovePercent
         } else {
-            val minScale = (Math.pow(mScale.toDouble(), position.toDouble())).toFloat()
-            val maxScale = (Math.pow(mScale.toDouble(), (position - 1).toDouble())).toFloat()
+            val minScale = (mScale.toDouble().pow(position.toDouble())).toFloat()
+            val maxScale = (mScale.toDouble().pow((position - 1).toDouble())).toFloat()
             scale = minScale + (maxScale - minScale) * firstMovePercent
             //只对最后一个 item 做透明度变化
             if (position == mVisibleCount) {
diff --git a/StackLayoutManager/src/main/java/com/littlemango/stacklayoutmanager/StackLayoutManager.kt b/StackLayoutManager/src/main/java/com/littlemango/stacklayoutmanager/StackLayoutManager.kt
index 5eef721..5c5ae25 100644
--- a/StackLayoutManager/src/main/java/com/littlemango/stacklayoutmanager/StackLayoutManager.kt
+++ b/StackLayoutManager/src/main/java/com/littlemango/stacklayoutmanager/StackLayoutManager.kt
@@ -6,6 +6,8 @@ import android.support.v7.widget.RecyclerView.SCROLL_STATE_DRAGGING
 import android.support.v7.widget.RecyclerView.SCROLL_STATE_IDLE
 import android.view.View
 import android.view.ViewGroup
+import kotlin.math.max
+import kotlin.math.min
 
 class StackLayoutManager(scrollOrientation: ScrollOrientation,
                           visibleCount: Int,
@@ -427,8 +429,8 @@ class StackLayoutManager(scrollOrientation: ScrollOrientation,
 
     private fun getValidOffset(expectOffset: Int): Int {
         return when(mScrollOrientation) {
-            ScrollOrientation.RIGHT_TO_LEFT, ScrollOrientation.LEFT_TO_RIGHT -> Math.max(Math.min(width * (itemCount - 1), expectOffset), 0)
-            else -> Math.max(Math.min(height * (itemCount - 1), expectOffset), 0)
+            ScrollOrientation.RIGHT_TO_LEFT, ScrollOrientation.LEFT_TO_RIGHT -> max(min(width * (itemCount - 1), expectOffset), 0)
+            else -> max(min(height * (itemCount - 1), expectOffset), 0)
         }
     }