diff --git a/src/game-logic/buildings.ts b/src/game-logic/buildings.ts
index 8cc1268..603a056 100644
--- a/src/game-logic/buildings.ts
+++ b/src/game-logic/buildings.ts
@@ -107,6 +107,36 @@ export const BUILDINGS = {
       fuel: 10, // fuel_production tech tree
     },
   },
+  shipyard: {
+    id: 'shipyard',
+    cost: {
+      minerals: 50, // cheap_buildings tech tree
+      alloys: 75, // cheap_buildings tech tree
+    },
+    upkeep: {
+      minerals: 10, // efficient_buildings tech tree
+      energy: 5, // efficient_buildings tech tree
+      fuel: 5, // efficient_buildings tech tree
+      alloys: 10, // efficient_buildings tech tree
+    },
+    production: {
+    },
+  },
+  fortress: {
+    id: 'fortress',
+    cost: {
+      minerals: 75, // cheap_buildings tech tree
+      alloys: 75, // cheap_buildings tech tree
+    },
+    upkeep: {
+      minerals: 5, // efficient_buildings tech tree
+      energy: 8, // efficient_buildings tech tree
+      fuel: 8, // efficient_buildings tech tree
+      alloys: 5, // efficient_buildings tech tree
+    },
+    production: {
+    },
+  },
 } as const satisfies Record<string, Building>;
 export type BuildingName = keyof typeof BUILDINGS;
 export const BUILDING_NAMES = Object.keys(BUILDINGS) as BuildingName[];
diff --git a/src/game-logic/technologies.ts b/src/game-logic/technologies.ts
index 63de1ae..6d0f512 100644
--- a/src/game-logic/technologies.ts
+++ b/src/game-logic/technologies.ts
@@ -319,6 +319,30 @@ export const TECHNOLOGIES: Record<string, Technology> = {
       },
     ],
   },
+  cheap_buildings_3: { // reduced advanced building costs
+    id: 'cheap_buildings_3',
+    tags: ['engineering', 'construction'],
+    cost: 4,
+    requires: ['cheap_buildings_2'],
+    effects: [
+      {
+        variable: 'buildings.shipyard.cost.alloys',
+        multiplier: 0.85,
+      },
+      {
+        variable: 'buildings.shipyard.cost.minerals',
+        multiplier: 0.85,
+      },
+      {
+        variable: 'buildings.fortress.cost.alloys',
+        multiplier: 0.85,
+      },
+      {
+        variable: 'buildings.fortress.cost.minerals',
+        multiplier: 0.85,
+      },
+    ],
+  },
 
   /** buildings: reduce energy upkeep */
   efficient_buildings_1: { // reduced basic building energy upkeep
@@ -340,6 +364,10 @@ export const TECHNOLOGIES: Record<string, Technology> = {
         variable: 'buildings.factory.upkeep.energy',
         multiplier: 0.85,
       },
+      {
+        variable: 'buildings.farm.upkeep.fuel',
+        multiplier: 0.85,
+      },
     ],
   },
   efficient_buildings_2: { // reduced advanced building energy upkeep
@@ -364,6 +392,18 @@ export const TECHNOLOGIES: Record<string, Technology> = {
         variable: 'buildings.exchange.upkeep.energy',
         multiplier: 0.85,
       },
+      {
+        variable: 'buildings.mine.upkeep.fuel',
+        multiplier: 0.85,
+      },
+      {
+        variable: 'buildings.shipyard.upkeep.fuel',
+        multiplier: 0.85,
+      },
+      {
+        variable: 'buildings.fortress.upkeep.fuel',
+        multiplier: 0.85,
+      },
     ],
   },
   efficient_buildings_3: {
@@ -377,19 +417,34 @@ export const TECHNOLOGIES: Record<string, Technology> = {
         multiplier: 0.85,
       },
       {
-        variable: 'buildings.mine.upkeep.fuel',
+        variable: 'buildings.research_lab.upkeep.consumer_goods',
         multiplier: 0.85,
       },
       {
-        variable: 'buildings.farm.upkeep.fuel',
+        variable: 'buildings.factory.upkeep.minerals',
         multiplier: 0.85,
       },
       {
-        variable: 'buildings.research_lab.upkeep.consumer_goods',
+        variable: 'buildings.shipyard.upkeep.alloys',
         multiplier: 0.85,
       },
       {
-        variable: 'buildings.factory.upkeep.minerals',
+        variable: 'buildings.shipyard.upkeep.energy',
+        multiplier: 0.85,
+      },{
+        variable: 'buildings.shipyard.upkeep.minerals',
+        multiplier: 0.85,
+      },
+      {
+        variable: 'buildings.fortress.upkeep.alloys',
+        multiplier: 0.85,
+      },
+      {
+        variable: 'buildings.fortress.upkeep.energy',
+        multiplier: 0.85,
+      },
+      {
+        variable: 'buildings.fortress.upkeep.minerals',
         multiplier: 0.85,
       },
     ],