Turret pattern rewrite

core/src/mindustry/entities/pattern/ShootAlternate.java

@@ -0,0 +1,18 @@
+package mindustry.entities.pattern;
+
+public class ShootAlternate extends ShootPattern{
+    /** number of barrels used for shooting. */
+    public int barrels = 2;
+    /** spread between barrels, in world units - not degrees. */
+    public float spread = 5f;
+    /** offset of barrel to start on */
+    public int barrelOffset = 0;
+
+    @Override
+    public void shoot(int totalShots, BulletHandler handler){
+        for(int i = 0; i < shots; i++){
+            float index = ((totalShots + i + barrelOffset) % barrels) - (barrels-1)/2f;
+            handler.shoot(index * spread, 0, 0f, firstShotDelay + shotDelay * i);
+        }
+    }
+}