System for controlling bullet movement

core/src/mindustry/entities/Mover.java

@@ -0,0 +1,9 @@
+package mindustry.entities;
+
+import arc.math.geom.*;
+import mindustry.gen.*;
+
+/** Applies custom movement to a bullet. */
+public interface Mover{
+    float move(Bullet bullet);
+}

core/src/mindustry/entities/bullet/BulletType.java

@@ -501,6 +501,11 @@ public class BulletType extends Content implements Cloneable{
         return create(owner, team, x, y, angle, -1, velocityScl, lifetimeScl, null);
     }
 
+
+    public @Nullable Bullet create(Entityc owner, Team team, float x, float y, float angle, float velocityScl, float lifetimeScl, Mover mover){
+        return create(owner, team, x, y, angle, -1, velocityScl, lifetimeScl, null, mover);
+    }
+
     public @Nullable Bullet create(Bullet parent, float x, float y, float angle){
         return create(parent.owner, parent.team, x, y, angle);
     }
@@ -514,6 +519,10 @@ public class BulletType extends Content implements Cloneable{
     }
 
     public @Nullable Bullet create(@Nullable Entityc owner, Team team, float x, float y, float angle, float damage, float velocityScl, float lifetimeScl, Object data){
+        return create(owner, team, x, y, angle, damage, velocityScl, lifetimeScl, data, null);
+    }
+
+    public @Nullable Bullet create(@Nullable Entityc owner, Team team, float x, float y, float angle, float damage, float velocityScl, float lifetimeScl, Object data, @Nullable Mover mover){
         if(spawnUnit != null){
             //don't spawn units clientside!
             if(!net.client()){
@@ -548,6 +557,7 @@ public class BulletType extends Content implements Cloneable{
         bullet.data = data;
         bullet.drag = drag;
         bullet.hitSize = hitSize;
+        bullet.mover = mover;
         bullet.damage = (damage < 0 ? this.damage : damage) * bullet.damageMultiplier();
         //reset trail
         if(bullet.trail != null){

core/src/mindustry/entities/comp/BulletComp.java

@@ -2,12 +2,14 @@ package mindustry.entities.comp;
 
 import arc.func.*;
 import arc.graphics.g2d.*;
+import arc.math.*;
 import arc.math.geom.*;
 import arc.struct.*;
 import arc.util.*;
 import mindustry.annotations.Annotations.*;
 import mindustry.content.*;
 import mindustry.core.*;
+import mindustry.entities.*;
 import mindustry.entities.bullet.*;
 import mindustry.game.*;
 import mindustry.game.Teams.*;
@@ -35,6 +37,7 @@ abstract class BulletComp implements Timedc, Damagec, Hitboxc, Teamc, Posc, Draw
     @ReadOnly
     private float rotation;
 
+    transient @Nullable Mover mover;
     transient boolean absorbed, hit;
     transient @Nullable Trail trail;
 
@@ -119,6 +122,12 @@ abstract class BulletComp implements Timedc, Damagec, Hitboxc, Teamc, Posc, Draw
 
     @Override
     public void update(){
+        if(mover != null){
+            float v = mover.move(self()) * Time.delta;
+            float ang = vel.angle();
+            vel.add(Angles.trnsx(ang, 0f, v), Angles.trnsy(ang, 0f, v)).limit(type.speed);
+        }
+
         type.update(self());
 
         if(type.collidesTiles && type.collides && type.collidesGround){