diff --git a/src/main.ts b/src/main.ts
index ea76509..16bb479 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -20,7 +20,7 @@ export const loop = errorMapper(() => {
         } else if (creep.memory.role == "Upgrader") {
             Upgrade(creep);
         } else if (creep.memory.role == "Builder") {
-            Build(creep);
+            Build(creep, STRUCTURE_CONTAINER);
         }
     }
 })
\ No newline at end of file
diff --git a/src/modules/builder.ts b/src/modules/builder.ts
index aacac22..c3c8b0d 100644
--- a/src/modules/builder.ts
+++ b/src/modules/builder.ts
@@ -1,6 +1,7 @@
-import { FindCapacity } from "./util";
+import { MAIN_SOURCE_ID } from "./setting";
+import { FindCapacity, GetConstructureSet, GetSource } from "./util";
 
-export function Build(creep: Creep) {
+export function Build(creep: Creep, structureType: string | null = null) {
     if (creep.memory.working && creep.store[RESOURCE_ENERGY] == 0) {
         creep.memory.working = false;
         creep.say("harvest")
@@ -10,7 +11,7 @@ export function Build(creep: Creep) {
         creep.say("builder")
     }
     if (creep.memory.working) {
-        let target = creep.room.find(FIND_CONSTRUCTION_SITES);
+        let target = GetConstructureSet(creep, structureType);
         if (target.length > 0) {
             if (creep.build(target[0]) == ERR_NOT_IN_RANGE) {
                 creep.moveTo(target[0], { visualizePathStyle: { stroke: "#ffaa00" } });
@@ -26,9 +27,9 @@ export function Build(creep: Creep) {
         }
     } else {
         creep.memory.working = false
-        let sources = creep.room.find(FIND_SOURCES);
-        if (creep.harvest(sources[0]) == ERR_NOT_IN_RANGE) {
-            creep.moveTo(sources[0], { visualizePathStyle: { stroke: "#ffaa00" } });
+        let source = GetSource(MAIN_SOURCE_ID);
+        if (creep.harvest(source) == ERR_NOT_IN_RANGE) {
+            creep.moveTo(source, { visualizePathStyle: { stroke: "#ffaa00" } });
         }
     }
 }
\ No newline at end of file
diff --git a/src/modules/harvester.ts b/src/modules/harvester.ts
index 9c4f4a7..ebe02aa 100644
--- a/src/modules/harvester.ts
+++ b/src/modules/harvester.ts
@@ -1,10 +1,11 @@
-import { FindCapacity } from "./util"
+import { FindCapacity, GetSource } from "./util"
+import { MAIN_SOURCE_ID } from "./setting";
 
 export function Harvest(creep: Creep) {
     if (creep.store.getFreeCapacity() > 0) {
-        let sources: Source[] = creep.room.find(FIND_SOURCES);
-        if (creep.harvest(sources[0]) == ERR_NOT_IN_RANGE) {
-            creep.moveTo(sources[0], { visualizePathStyle: { stroke: "#ffaa00" } });
+        let source: Source = GetSource(MAIN_SOURCE_ID);
+        if (creep.harvest(source) == ERR_NOT_IN_RANGE) {
+            creep.moveTo(source, { visualizePathStyle: { stroke: "#ffaa00" } });
         }
     } else {
         let targets = FindCapacity(creep);
diff --git a/src/modules/setting.ts b/src/modules/setting.ts
index c863a2c..e740195 100644
--- a/src/modules/setting.ts
+++ b/src/modules/setting.ts
@@ -1,9 +1,13 @@
-let HARVESTER_COUNT: number = 4;
+let HARVESTER_COUNT: number = 2;
 let BUILDER_COUNT: number = 3;
-let UPGRADER_COUNT: number = 6;
+let UPGRADER_COUNT: number = 5;
+
+let MAIN_SOURCE_ID: Id<Source> = "ef990774d80108c" as Id<Source>;
+
 export {
     HARVESTER_COUNT,
     BUILDER_COUNT,
-    UPGRADER_COUNT
+    UPGRADER_COUNT,
+    MAIN_SOURCE_ID,
 }
 
diff --git a/src/modules/upgrader.ts b/src/modules/upgrader.ts
index c3cb227..c170709 100644
--- a/src/modules/upgrader.ts
+++ b/src/modules/upgrader.ts
@@ -1,3 +1,6 @@
+import { MAIN_SOURCE_ID } from "./setting";
+import { GetSource } from "./util";
+
 /**@param {Creep} creep */
 export function Upgrade(creep: Creep) {
     if (creep.memory.working && creep.store[RESOURCE_ENERGY] == 0) {
@@ -15,9 +18,9 @@ export function Upgrade(creep: Creep) {
         }
     }
     else {
-        var sources = creep.room.find(FIND_SOURCES);
-        if (creep.harvest(sources[0]) == ERR_NOT_IN_RANGE) {
-            creep.moveTo(sources[0], { visualizePathStyle: { stroke: '#ffaa00' } });
+        var source = GetSource(MAIN_SOURCE_ID);
+        if (creep.harvest(source) == ERR_NOT_IN_RANGE) {
+            creep.moveTo(source, { visualizePathStyle: { stroke: '#ffaa00' } });
         }
     }
 }
\ No newline at end of file
diff --git a/src/modules/util.ts b/src/modules/util.ts
index 9e4c898..2f91288 100644
--- a/src/modules/util.ts
+++ b/src/modules/util.ts
@@ -1,12 +1,25 @@
-export function FindCapacity(creep: Creep) {
+export function FindCapacity(creep: Creep): AnyStructure[] {
     return creep.room.find(FIND_STRUCTURES, {
         filter: (structure: StructureSpawn | StructureExtension) => {
             let type = structure.structureType;
             return (
                 (type == STRUCTURE_EXTENSION ||
                     type == STRUCTURE_SPAWN) &&
-                    structure.store.getFreeCapacity(RESOURCE_ENERGY) as number > 0
+                structure.store.getFreeCapacity(RESOURCE_ENERGY) as number > 0
             )
         }
     })
+}
+
+export function GetSource(sourceId: Id<Source> | null): Source {
+    return Game.getObjectById(sourceId);
+}
+
+export function GetConstructureSet(creep: Creep, structureType: string | null = null): ConstructionSite<BuildableStructureConstant>[] {
+    return creep.room.find(FIND_CONSTRUCTION_SITES, {
+        filter: (structure: Structure) => {
+            if (structureType == null) return true;
+            return structure.structureType == structureType;
+        }
+    })
 }
\ No newline at end of file