Added underflow gates

core/assets/bundles/bundle.properties

@@ -944,6 +944,7 @@ block.message.name = Message
 block.illuminator.name = Illuminator
 block.illuminator.description = A small, compact, configurable light source. Requires power to function.
 block.overflow-gate.name = Overflow Gate
+block.underflow-gate.name = Underflow Gate
 block.silicon-smelter.name = Silicon Smelter
 block.phase-weaver.name = Phase Weaver
 block.pulverizer.name = Pulverizer
@@ -1174,6 +1175,7 @@ block.inverted-sorter.description = Processes items like a standard sorter, but
 block.router.description = Accepts items, then outputs them to up to 3 other directions equally. Useful for splitting the materials from one source to multiple targets.\n\n[scarlet]Never use next to production inputs, as they will get clogged by output.[]
 block.distributor.description = An advanced router. Splits items to up to 7 other directions equally.
 block.overflow-gate.description = Only outputs to the left and right if the front path is blocked.
+block.underflow-gate.description = The opposite of an overflow gate. Outputs to the front if the left and right paths are blocked.
 block.mass-driver.description = The ultimate item transport block. Collects several items and then shoots them to another mass driver over a long range. Requires power to operate.
 block.mechanical-pump.description = A cheap pump with slow output, but no power consumption.
 block.rotary-pump.description = An advanced pump. Pumps more liquid, but requires power.

core/assets/icons/icons.properties

@@ -217,3 +217,4 @@
 63527=slag|liquid-slag-icon
 63526=oil|liquid-oil-icon
 63525=cryofluid|liquid-cryofluid-icon
+63524=underflow-gate|block-underflow-gate-medium

core/src/mindustry/content/Blocks.java

@@ -57,7 +57,7 @@ public class Blocks implements ContentList{
     scrapWall, scrapWallLarge, scrapWallHuge, scrapWallGigantic, thruster, //ok, these names are getting ridiculous, but at least I don't have humongous walls yet
 
     //transport
-    conveyor, titaniumConveyor, armoredConveyor, distributor, junction, itemBridge, phaseConveyor, sorter, invertedSorter, router, overflowGate, massDriver,
+    conveyor, titaniumConveyor, armoredConveyor, distributor, junction, itemBridge, phaseConveyor, sorter, invertedSorter, router, overflowGate, underflowGate, massDriver,
 
     //liquids
     mechanicalPump, rotaryPump, thermalPump, conduit, pulseConduit, platedConduit, liquidRouter, liquidTank, liquidJunction, bridgeConduit, phaseConduit,
@@ -945,6 +945,12 @@ public class Blocks implements ContentList{
             buildCostMultiplier = 3f;
         }};
 
+        underflowGate = new OverflowGate("underflow-gate"){{
+            requirements(Category.distribution, ItemStack.with(Items.lead, 2, Items.copper, 4));
+            buildCostMultiplier = 3f;
+            invert = true;
+        }};
+
         massDriver = new MassDriver("mass-driver"){{
             requirements(Category.distribution, ItemStack.with(Items.titanium, 125, Items.silicon, 75, Items.lead, 125, Items.thorium, 50));
             size = 3;

core/src/mindustry/world/blocks/distribution/OverflowGate.java

@@ -11,6 +11,7 @@ import java.io.*;
 
 public class OverflowGate extends Block{
     public float speed = 1f;
+    public boolean invert = false;
 
     public OverflowGate(String name){
         super(name);
@@ -76,21 +77,22 @@ public class OverflowGate extends Block{
         update(tile);
     }
 
-    Tile getTileTarget(Tile tile, Item item, Tile src, boolean flip){
+    public Tile getTileTarget(Tile tile, Item item, Tile src, boolean flip){
         int from = tile.relativeTo(src.x, src.y);
         if(from == -1) return null;
         Tile to = tile.getNearby((from + 2) % 4);
         if(to == null) return null;
         Tile edge = Edges.getFacingEdge(tile, to);
+        boolean canForward = to.block().acceptItem(item, to, edge) && to.getTeam() == tile.getTeam() && !(to.block() instanceof OverflowGate);
 
-        if(!to.block().acceptItem(item, to, edge) || to.getTeam() != tile.getTeam() || (to.block() instanceof OverflowGate)){
+        if(!canForward || invert){
             Tile a = tile.getNearby(Mathf.mod(from - 1, 4));
             Tile b = tile.getNearby(Mathf.mod(from + 1, 4));
             boolean ac = a != null && a.block().acceptItem(item, a, edge) && !(a.block() instanceof OverflowGate) && a.getTeam() == tile.getTeam();
             boolean bc = b != null && b.block().acceptItem(item, b, edge) && !(b.block() instanceof OverflowGate) && b.getTeam() == tile.getTeam();
 
             if(!ac && !bc){
-                return null;
+                return invert && canForward ? to : null;
             }
 
             if(ac && !bc){