diff --git a/build.gradle b/build.gradle
index 2a96889..7634d3c 100644
--- a/build.gradle
+++ b/build.gradle
@@ -6,7 +6,7 @@ plugins {
 }
 
 group = 'me.skymc'
-version = '5.16'
+version = '5.17'
 
 sourceCompatibility = 1.8
 targetCompatibility = 1.8
diff --git a/src/main/scala/io/izzel/taboolib/Version.java b/src/main/scala/io/izzel/taboolib/Version.java
index 996e8bc..90d8970 100644
--- a/src/main/scala/io/izzel/taboolib/Version.java
+++ b/src/main/scala/io/izzel/taboolib/Version.java
@@ -10,7 +10,7 @@ import java.util.Arrays;
  */
 public enum Version {
 
-    v1_7(10700), v1_8(10800), v1_9(10900), v1_10(11000), v1_11(11100), v1_12(11200), v1_13(11300), v1_14(11400), v1_15(11500), vNull(0);
+    v1_7(10700), v1_8(10800), v1_9(10900), v1_10(11000), v1_11(11100), v1_12(11200), v1_13(11300), v1_14(11400), v1_15(11500), v1_16(11600), vNull(0);
 
     private int versionInt;
 
diff --git a/src/main/scala/io/izzel/taboolib/module/command/lite/CommandBuilder.java b/src/main/scala/io/izzel/taboolib/module/command/lite/CommandBuilder.java
index 4bb4863..a19188d 100644
--- a/src/main/scala/io/izzel/taboolib/module/command/lite/CommandBuilder.java
+++ b/src/main/scala/io/izzel/taboolib/module/command/lite/CommandBuilder.java
@@ -18,8 +18,8 @@ import java.util.UUID;
  */
 public class CommandBuilder {
 
-    public static final CompleterTab EMPTY_COMPLETER_TAB = ((sender, args) -> new ArrayList<>());
-    public static final CompleterCommand EMPTY_COMPLETER_COMMAND = ((sender, args) -> {});
+    public static final CompleterCommand EMPTY_COMPLETER_COMMAND = ((sender, args) -> {
+    });
 
     private String command;
     private Plugin plugin;
@@ -28,7 +28,7 @@ public class CommandBuilder {
     private List<String> aliases;
     private String permission;
     private String permissionMessage;
-    private CompleterTab completerTab = EMPTY_COMPLETER_TAB;
+    private CompleterTab completerTab;
     private CompleterCommand completerCommand = EMPTY_COMPLETER_COMMAND;
     private boolean forceRegister;
     private boolean build;
@@ -106,7 +106,6 @@ public class CommandBuilder {
         Preconditions.checkNotNull(plugin, "缺少 \"plugin\" 部分");
         Preconditions.checkNotNull(command, "缺少 \"command\" 部分");
         Preconditions.checkNotNull(completerCommand, "缺少 \"CompleterCommand\" 部分");
-        Preconditions.checkNotNull(completerTab, "缺少 \"CompleterTab\" 部分");
         if (forceRegister) {
             TCommandHandler.getKnownCommands().remove(command);
         }
@@ -118,18 +117,20 @@ public class CommandBuilder {
                 aliases,
                 permission,
                 permissionMessage,
-                (sender, command, s, args) -> {
-                    completerCommand.execute(sender, args);
-                    return true;
-                },
-                (sender, command, s, args) -> {
-                    try {
-                        return completerTab.execute(sender, args);
-                    } catch (Throwable t) {
-                        t.printStackTrace();
-                    }
-                    return null;
-                });
+                completerCommand == null ? null :
+                        (sender, command, s, args) -> {
+                            completerCommand.execute(sender, args);
+                            return true;
+                        },
+                completerTab == null ? null :
+                        (sender, command, s, args) -> {
+                            try {
+                                return completerTab.execute(sender, args);
+                            } catch (Throwable t) {
+                                t.printStackTrace();
+                            }
+                            return null;
+                        });
         build = true;
         return this;
     }
diff --git a/src/main/scala/io/izzel/taboolib/module/nms/NMS.java b/src/main/scala/io/izzel/taboolib/module/nms/NMS.java
index 3a7bb58..5b2398a 100644
--- a/src/main/scala/io/izzel/taboolib/module/nms/NMS.java
+++ b/src/main/scala/io/izzel/taboolib/module/nms/NMS.java
@@ -7,11 +7,14 @@ import io.izzel.taboolib.module.nms.nbt.Attribute;
 import io.izzel.taboolib.module.nms.nbt.NBTAttribute;
 import io.izzel.taboolib.module.nms.nbt.NBTCompound;
 import io.izzel.taboolib.module.nms.nbt.NBTList;
+import org.bukkit.Location;
 import org.bukkit.Particle;
 import org.bukkit.block.Block;
 import org.bukkit.entity.Entity;
 import org.bukkit.entity.Player;
+import org.bukkit.event.entity.ProjectileHitEvent;
 import org.bukkit.inventory.ItemStack;
+import org.bukkit.util.Vector;
 
 import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
@@ -78,4 +81,8 @@ public abstract class NMS {
     abstract public Position fromBlockPosition(Object blockPosition);
 
     abstract public void openSignEditor(Player player, Block block);
+
+    abstract public boolean inBoundingBox(Entity entity, Vector vector);
+
+    abstract public Location getLastLocation(ProjectileHitEvent event);
 }
diff --git a/src/main/scala/io/izzel/taboolib/module/nms/NMSImpl.java b/src/main/scala/io/izzel/taboolib/module/nms/NMSImpl.java
index 4d064a1..d6b00c7 100644
--- a/src/main/scala/io/izzel/taboolib/module/nms/NMSImpl.java
+++ b/src/main/scala/io/izzel/taboolib/module/nms/NMSImpl.java
@@ -16,6 +16,7 @@ import net.minecraft.server.v1_13_R2.IRegistry;
 import net.minecraft.server.v1_8_R3.NBTBase;
 import net.minecraft.server.v1_8_R3.*;
 import org.bukkit.Bukkit;
+import org.bukkit.Location;
 import org.bukkit.Particle;
 import org.bukkit.World;
 import org.bukkit.block.Block;
@@ -28,8 +29,10 @@ import org.bukkit.craftbukkit.v1_8_R3.inventory.CraftItemStack;
 import org.bukkit.entity.Entity;
 import org.bukkit.entity.Player;
 import org.bukkit.entity.Villager;
+import org.bukkit.event.entity.ProjectileHitEvent;
 import org.bukkit.inventory.ItemStack;
 import org.bukkit.inventory.meta.PotionMeta;
+import org.bukkit.util.Vector;
 
 import java.lang.reflect.Field;
 import java.util.List;
@@ -404,4 +407,43 @@ public class NMSImpl extends NMS {
         }
         return null;
     }
+
+    @Override
+    public boolean inBoundingBox(Entity entity, Vector vector) {
+        if (Version.isAfter(Version.v1_14)) {
+            return ((org.bukkit.craftbukkit.v1_14_R1.entity.CraftEntity) entity).getHandle().getBoundingBox().c(new net.minecraft.server.v1_14_R1.Vec3D(vector.getX(), vector.getY(), vector.getZ()));
+        } else {
+            return ((org.bukkit.craftbukkit.v1_12_R1.entity.CraftEntity) entity).getHandle().getBoundingBox().b(new net.minecraft.server.v1_12_R1.Vec3D(vector.getX(), vector.getY(), vector.getZ()));
+        }
+    }
+
+    @Override
+    public Location getLastLocation(ProjectileHitEvent event) {
+        Vector vector = event.getEntity().getVelocity().normalize().multiply(0.1);
+        Vector vectorEntity = event.getEntity().getLocation().toVector();
+        if (event.getHitBlock() != null) {
+            double i = 0;
+            double length = event.getHitBlock().getLocation().add(0.5, 0.5, 0.5).distance(event.getEntity().getLocation()) * 2;
+            while (i < length) {
+                Location location = vectorEntity.toLocation(event.getHitBlock().getWorld());
+                if (location.getBlock().getLocation().equals(event.getHitBlock().getLocation())) {
+                    return location;
+                }
+                vectorEntity.add(vector);
+                i += 0.1;
+            }
+        }
+        if (event.getHitEntity() != null) {
+            double i = 0;
+            double length = event.getHitEntity().getLocation().distance(event.getEntity().getLocation()) * 2;
+            while (i < length) {
+                if (inBoundingBox(event.getHitEntity(), vectorEntity)) {
+                    return vectorEntity.toLocation(event.getHitEntity().getWorld());
+                }
+                vectorEntity.add(vector);
+                i += 0.1;
+            }
+        }
+        return null;
+    }
 }
diff --git a/src/main/scala/io/izzel/taboolib/util/Files.java b/src/main/scala/io/izzel/taboolib/util/Files.java
index a6d5f93..035f5b7 100644
--- a/src/main/scala/io/izzel/taboolib/util/Files.java
+++ b/src/main/scala/io/izzel/taboolib/util/Files.java
@@ -319,6 +319,15 @@ public class Files {
         }
     }
 
+    public static void writeAppend(File file, WriteHandle writeHandle) {
+        try (FileWriter fileWriter = new FileWriter(file, true); BufferedWriter bufferedWriter = new BufferedWriter(fileWriter)) {
+            writeHandle.write(bufferedWriter);
+            bufferedWriter.flush();
+        } catch (Throwable t) {
+            t.printStackTrace();
+        }
+    }
+
     public static void write(OutputStream out, WriteHandle writeHandle) {
         try (OutputStreamWriter outputStreamWriter = new OutputStreamWriter(out); BufferedWriter bufferedWriter = new BufferedWriter(outputStreamWriter)) {
             writeHandle.write(bufferedWriter);
diff --git a/src/main/scala/io/izzel/taboolib/util/lite/Effects.java b/src/main/scala/io/izzel/taboolib/util/lite/Effects.java
index 8ba435d..c4e074a 100644
--- a/src/main/scala/io/izzel/taboolib/util/lite/Effects.java
+++ b/src/main/scala/io/izzel/taboolib/util/lite/Effects.java
@@ -10,11 +10,13 @@ import org.bukkit.entity.Player;
 import org.bukkit.inventory.ItemStack;
 import org.bukkit.material.MaterialData;
 import org.bukkit.util.NumberConversions;
+import org.bukkit.util.Vector;
 
 import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.function.Consumer;
 
 /**
  * @Author sky
@@ -81,6 +83,28 @@ public class Effects {
         return Particle.FLAME;
     }
 
+    public static void buildLine(Location locA, Location locB, Consumer<Location> action) {
+        buildLine(locA, locB, action, 0.25);
+    }
+
+    public static void buildLine(Location locA, Location locB, Consumer<Location> action, double interval) {
+        Vector vectorAB = locB.clone().subtract(locA).toVector();
+        double vectorLength = vectorAB.length();
+        vectorAB.normalize();
+        for (double i = 0; i < vectorLength; i += interval) {
+            action.accept(locA.clone().add(vectorAB.clone().multiply(i)));
+        }
+    }
+
+    public static void buildPolygon(Location center, double range, double interval, Consumer<Location> action) {
+        for (double i = 0; i < 360; i += (360 / interval)) {
+            double radians = Math.toRadians(i);
+            double cos = Math.cos(radians) * range;
+            double sin = Math.sin(radians) * range;
+            action.accept(center.clone().add(cos, 0, sin));
+        }
+    }
+
     Effects() {
     }