diff --git a/src/builder.ts b/src/builder.ts
index 65d23a9..a8aa13d 100644
--- a/src/builder.ts
+++ b/src/builder.ts
@@ -1,33 +1,49 @@
+interface BuilderMemory extends CreepMemory {
+  building: boolean | undefined;
+  sourceNum: number | undefined;
+}
+
+function randomIntInRange(min: number, max: number): number {
+  const delta = max - min;
+  return Math.floor(Math.random() * delta) + min;
+}
+
 export function runAsBuilder(creep: Creep) {
-  const memory = creep.memory as CreepMemory & { building: boolean | undefined };
+  const memory = creep.memory as BuilderMemory;
 
   if (memory.building && creep.store[RESOURCE_ENERGY] === 0) {
     memory.building = false;
-    creep.say('🔄 harvest');
   }
 
   if (!memory.building && creep.store.getFreeCapacity() === 0) {
     memory.building = true;
-    creep.say('🚧 build');
+  }
+
+  if (memory.sourceNum === undefined) {
+    const sources = creep.room.find(FIND_SOURCES);
+    memory.sourceNum = randomIntInRange(0, sources.length);
   }
 
   if (memory.building) {
     const targets = creep.room.find(FIND_CONSTRUCTION_SITES);
     if (targets.length > 0) {
       if (creep.build(targets[0]) == ERR_NOT_IN_RANGE) {
+        creep.say('🚧 build');
         creep.moveTo(targets[0], { visualizePathStyle: { stroke: '#ffffff' } });
       }
     } else {
       const spawns = creep.room.find(FIND_MY_SPAWNS);
       if (spawns.length > 0) {
-        creep.say('to spawn');
+        creep.say('To spawn');
         creep.moveTo(spawns[0]);
       }
     }
   } else {
     const sources = creep.room.find(FIND_SOURCES);
-    if (creep.harvest(sources[0]) == ERR_NOT_IN_RANGE) {
-      creep.moveTo(sources[0], { visualizePathStyle: { stroke: '#ffaa00' } });
+    const sourceNum = memory.sourceNum;
+    if (creep.harvest(sources[sourceNum]) == ERR_NOT_IN_RANGE) {
+      creep.say('🔄 harvest ' + sourceNum);
+      creep.moveTo(sources[sourceNum], { visualizePathStyle: { stroke: '#ffaa00' } });
     }
   }
 }
diff --git a/src/main.ts b/src/main.ts
index 307b6b4..9beede6 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -39,7 +39,7 @@ export const loop = ErrorMapper.wrapLoop(() => {
 
   makeCreep(CreepRole.HARVESTER, 1);
   makeCreep(CreepRole.UPGRADER, 3);
-  makeCreep(CreepRole.BUILDER, 2);
+  makeCreep(CreepRole.BUILDER, 4);
 
   // Process current creeps
   for (let name in Game.creeps) {