diff --git a/apps/api/package.json b/apps/api/package.json
index ab014fc..20bad3c 100644
--- a/apps/api/package.json
+++ b/apps/api/package.json
@@ -8,11 +8,13 @@
         "start": "bun run src/index.ts"
     },
     "dependencies": {
-        "@elysiajs/cors": "^1.4.2",
-        "elysia": "^1.4.28",
-        "zipcodes-us": "^1.1.3",
         "@blade-and-brawn/calculator": "workspace:*",
         "@blade-and-brawn/commerce": "workspace:*",
-        "ml-levenberg-marquardt": "^5.0.1"
+        "@blade-and-brawn/domain": "workspace:*",
+        "@elysiajs/cors": "^1.4.2",
+        "elysia": "^1.4.29",
+        "ml-levenberg-marquardt": "^5.0.1",
+        "zipcodes-us": "^1.1.3",
+        "zod": "^4.4.3"
     }
 }
diff --git a/apps/api/src/index.ts b/apps/api/src/index.ts
index af52bec..5b850a4 100644
--- a/apps/api/src/index.ts
+++ b/apps/api/src/index.ts
@@ -2,9 +2,14 @@ import {
     DEFAULT_STANDARDS_DATA,
     LevelCalculator,
     Standards,
+} from "@blade-and-brawn/calculator";
+
+import {
+    ActivityPerformanceSchema,
+    PlayerSchema,
     type ActivityPerformance,
     type Player,
-} from "@blade-and-brawn/calculator";
+} from "@blade-and-brawn/domain"
 import { cors } from "@elysiajs/cors";
 import { Elysia, NotFoundError } from "elysia";
 import {
@@ -16,6 +21,7 @@ import {
     FetchError,
 } from "@blade-and-brawn/commerce";
 import zipcodesUs from "zipcodes-us";
+import z from "zod";
 
 const levelCalculator = new LevelCalculator(
     new Standards(DEFAULT_STANDARDS_DATA),
@@ -25,13 +31,18 @@ export const app = new Elysia()
     .use(
         cors({
             origin: [
-                // bladeandbrawn.com (apex + any subdomain)
+                // WEBSITE
+                // -----------
+                // production
                 /^https?:\/\/([a-z0-9-]+\.)?bladeandbrawn\.com$/i,
-                // Webflow preview domains
+                // testing
                 /^https?:\/\/([a-z0-9-]+\.)?bladeandbrawn\.webflow\.io$/i,
-                // Fly app host (this one already works)
+
+                // PORTAL
+                // -----------
+                // production
                 /^https?:\/\/blade-and-brawn\.fly\.dev$/i,
-                // Local dev portal
+                // development
                 "http://localhost:5173",
             ],
         }),
@@ -65,14 +76,9 @@ export const app = new Elysia()
 
     // CALCULATOR
 
-    .post("/calculate", async ({ body, query }) => {
-        interface CalcRequest {
-            player: Player;
-            activityPerformances: ActivityPerformance[];
-        }
-        const { player, activityPerformances } = body as CalcRequest;
+    .post("/calculate", async ({ body }) => {
         const output = {
-            levels: levelCalculator.calculate(player, activityPerformances),
+            levels: levelCalculator.calculate(body.player, body.activityPerformances),
         };
 
         // console.log({ log: query?.log });
@@ -85,6 +91,11 @@ export const app = new Elysia()
         // }
 
         return output;
+    }, {
+        body: z.object({
+            player: PlayerSchema,
+            activityPerformances: z.array(ActivityPerformanceSchema)
+        })
     })
 
     // COMMERCE
@@ -93,18 +104,26 @@ export const app = new Elysia()
         app
             .group("/sync", (app) =>
                 app
-                    .get("/", async ({}) => SyncService.state)
-                    .post("/:printfulProductId?", async ({ params, set }) => {
+                    // Sync status
+                    .get("/", async ({ }) => SyncService.state)
+                    // Full sync
+                    .post("/", async ({ set }) => {
                         if (SyncService.state.isSyncing) {
                             set.status = 409;
                             return { error: "Sync already in progress" };
                         }
-                        const printfulProductId = params.printfulProductId
-                            ? +params.printfulProductId
-                            : undefined;
-                        await SyncService.sync(printfulProductId);
+                        await SyncService.sync();
                         return { ok: true };
-                    }),
+                    })
+                    // Per-product sync
+                    .post("/:printfulProductId", async ({ params, set }) => {
+                        if (SyncService.state.isSyncing) {
+                            set.status = 409;
+                            return { error: "Sync already in progress" };
+                        }
+                        await SyncService.sync(params.printfulProductId);
+                        return { ok: true };
+                    }, { params: z.object({ printfulProductId: z.number() }) }),
             )
             .get("/:printfulProductId", async ({ params }) => {
                 const printfulProductId = +params.printfulProductId;
diff --git a/apps/portal/package.json b/apps/portal/package.json
index 9caa47c..8ce31d7 100644
--- a/apps/portal/package.json
+++ b/apps/portal/package.json
@@ -2,7 +2,7 @@
     "name": "@blade-and-brawn/portal",
     "type": "module",
     "devDependencies": {
-        "@sveltejs/kit": "^2.65.1",
+        "@sveltejs/kit": "^2.66.0",
         "@sveltejs/vite-plugin-svelte": "^6.2.4",
         "@types/bun": "^1.3.14",
         "svelte": "^5.56.3",
@@ -22,9 +22,9 @@
     "dependencies": {
         "@tailwindcss/vite": "^4.3.1",
         "daisyui": "^5.5.23",
-        "memoirist": "^0.4.0",
         "tailwindcss": "^4.3.1",
         "@blade-and-brawn/calculator": "workspace:*",
-        "@blade-and-brawn/commerce": "workspace:*"
+        "@blade-and-brawn/commerce": "workspace:*",
+        "@blade-and-brawn/domain": "workspace:*"
     }
 }
diff --git a/apps/portal/src/lib/components/PlayersTable.svelte b/apps/portal/src/lib/components/PlayersTable.svelte
index 3557404..46b9dff 100644
--- a/apps/portal/src/lib/components/PlayersTable.svelte
+++ b/apps/portal/src/lib/components/PlayersTable.svelte
@@ -1,16 +1,18 @@
 <script lang="ts">
     import {
         LevelCalculator,
+        type LevelCalculatorOutput,
+        type Standards,
+    } from "@blade-and-brawn/calculator";
+    import {
         Activity,
         Attribute,
         Gender,
         lbToKg,
         range,
-        type LevelCalculatorOutput,
-        type Standards,
         type ActivityPerformance,
         type Player,
-    } from "@blade-and-brawn/calculator";
+    } from "@blade-and-brawn/domain";
 
     interface CalcData {
         levels?: LevelCalculatorOutput;
diff --git a/apps/portal/src/lib/components/StandardsTable.svelte b/apps/portal/src/lib/components/StandardsTable.svelte
index 3f92c6c..da93d4d 100644
--- a/apps/portal/src/lib/components/StandardsTable.svelte
+++ b/apps/portal/src/lib/components/StandardsTable.svelte
@@ -1,14 +1,16 @@
 <script lang="ts">
     import {
         Standards,
+        type Standard,
+        type StandardsConfig,
+    } from "@blade-and-brawn/calculator";
+    import {
         Activity,
         cmToIn,
         kgToLb,
         range,
         type Metrics,
-        type Standard,
-        type StandardsConfig,
-    } from "@blade-and-brawn/calculator";
+    } from "@blade-and-brawn/domain";
 
     interface Props {
         allStandards: Standards;
diff --git a/apps/portal/src/routes/calculator/+page.svelte b/apps/portal/src/routes/calculator/+page.svelte
index a11470b..b9d089c 100644
--- a/apps/portal/src/routes/calculator/+page.svelte
+++ b/apps/portal/src/routes/calculator/+page.svelte
@@ -1,13 +1,15 @@
 <script lang="ts">
     import {
-        Activity,
         DEFAULT_STANDARDS_DATA,
-        Gender,
-        lbToKg,
         Standards,
-        type Metrics,
         type StandardsConfig,
     } from "@blade-and-brawn/calculator";
+    import {
+        Activity,
+        Gender,
+        lbToKg,
+        type Metrics,
+    } from "@blade-and-brawn/domain";
     import StandardsTable from "$lib/components/StandardsTable.svelte";
     import PlayersTable from "$lib/components/PlayersTable.svelte";
 
@@ -15,6 +17,7 @@
 
     const defaultStandards = new Standards(DEFAULT_STANDARDS_DATA);
 
+    // TODO: try to clean this up
     let input = $state({
         activity: Activity.BenchPress,
         metrics: {
diff --git a/bun.lock b/bun.lock
index d9a9990..ae84c73 100644
--- a/bun.lock
+++ b/bun.lock
@@ -16,10 +16,12 @@
       "dependencies": {
         "@blade-and-brawn/calculator": "workspace:*",
         "@blade-and-brawn/commerce": "workspace:*",
+        "@blade-and-brawn/domain": "workspace:*",
         "@elysiajs/cors": "^1.4.2",
-        "elysia": "^1.4.28",
+        "elysia": "^1.4.29",
         "ml-levenberg-marquardt": "^5.0.1",
         "zipcodes-us": "^1.1.3",
+        "zod": "^4.4.3",
       },
     },
     "apps/portal": {
@@ -27,26 +29,27 @@
       "dependencies": {
         "@blade-and-brawn/calculator": "workspace:*",
         "@blade-and-brawn/commerce": "workspace:*",
-        "@tailwindcss/vite": "^4.2.1",
-        "daisyui": "^5.5.19",
-        "memoirist": "^0.4.0",
-        "tailwindcss": "^4.2.1",
+        "@blade-and-brawn/domain": "workspace:*",
+        "@tailwindcss/vite": "^4.3.1",
+        "daisyui": "^5.5.23",
+        "tailwindcss": "^4.3.1",
       },
       "devDependencies": {
-        "@sveltejs/kit": "^2.54.0",
+        "@sveltejs/kit": "^2.66.0",
         "@sveltejs/vite-plugin-svelte": "^6.2.4",
-        "@types/bun": "^1.3.10",
-        "svelte": "^5.53.10",
+        "@types/bun": "^1.3.14",
+        "svelte": "^5.56.3",
         "svelte-adapter-bun": "^0.5.2",
-        "svelte-check": "^4.4.5",
+        "svelte-check": "^4.6.0",
         "typescript": "^5.9.3",
-        "vite": "^7.3.1",
+        "vite": "^7.3.5",
       },
     },
     "packages/calculator": {
       "name": "@blade-and-brawn/calculator",
       "version": "0.0.0",
       "dependencies": {
+        "@blade-and-brawn/domain": "workspace:*",
         "ml-levenberg-marquardt": "^5.0.0",
       },
     },
@@ -54,6 +57,14 @@
       "name": "@blade-and-brawn/commerce",
       "version": "0.0.0",
     },
+    "packages/domain": {
+      "name": "@blade-and-brawn/domain",
+      "version": "0.0.0",
+      "dependencies": {
+        "@blade-and-brawn/domain": "workspace:*",
+        "zod": "^4.4.3",
+      },
+    },
   },
   "packages": {
     "@blade-and-brawn/api": ["@blade-and-brawn/api@workspace:apps/api"],
@@ -62,6 +73,8 @@
 
     "@blade-and-brawn/commerce": ["@blade-and-brawn/commerce@workspace:packages/commerce"],
 
+    "@blade-and-brawn/domain": ["@blade-and-brawn/domain@workspace:packages/domain"],
+
     "@blade-and-brawn/portal": ["@blade-and-brawn/portal@workspace:apps/portal"],
 
     "@borewit/text-codec": ["@borewit/text-codec@0.2.1", "", {}, "sha512-k7vvKPbf7J2fZ5klGRD9AeKfUvojuZIQ3BT5u7Jfv+puwXkUBUT5PVyMDfJZpy30CBDXGMgw7fguK/lpOMBvgw=="],
@@ -188,7 +201,7 @@
 
     "@sveltejs/acorn-typescript": ["@sveltejs/acorn-typescript@1.0.10", "", { "peerDependencies": { "acorn": "^8.9.0" } }, "sha512-4WfKk68eTih+MiJD4fSbxN7E8kVBmTMPWHUPYjvl2N0rMs53YLTT8/YjKU5Dtnz5LqDjl7LEw4U7lXR2W3J5WA=="],
 
-    "@sveltejs/kit": ["@sveltejs/kit@2.65.1", "", { "dependencies": { "@standard-schema/spec": "^1.0.0", "@sveltejs/acorn-typescript": "^1.0.9", "@types/cookie": "^0.6.0", "acorn": "^8.16.0", "cookie": "^0.6.0", "devalue": "^5.8.1", "esm-env": "^1.2.2", "kleur": "^4.1.5", "magic-string": "^0.30.5", "mrmime": "^2.0.0", "set-cookie-parser": "^3.0.0", "sirv": "^3.0.0" }, "peerDependencies": { "@opentelemetry/api": "^1.0.0", "@sveltejs/vite-plugin-svelte": "^3.0.0 || ^4.0.0-next.1 || ^5.0.0 || ^6.0.0-next.0 || ^7.0.0", "svelte": "^4.0.0 || ^5.0.0-next.0", "typescript": "^5.3.3 || ^6.0.0", "vite": "^5.0.3 || ^6.0.0 || ^7.0.0-beta.0 || ^8.0.0" }, "optionalPeers": ["@opentelemetry/api", "typescript"], "bin": { "svelte-kit": "svelte-kit.js" } }, "sha512-Sa1rFYYqBB+zv3rIxAg/CsFskR/x4aj5BY/hvLxBd9r/mqbipxM945As1K3PqsDicJAyekPR0BlWoVIiw2OHYg=="],
+    "@sveltejs/kit": ["@sveltejs/kit@2.66.0", "", { "dependencies": { "@standard-schema/spec": "^1.0.0", "@sveltejs/acorn-typescript": "^1.0.9", "@types/cookie": "^0.6.0", "acorn": "^8.16.0", "cookie": "^0.6.0", "devalue": "^5.8.1", "esm-env": "^1.2.2", "kleur": "^4.1.5", "magic-string": "^0.30.5", "mrmime": "^2.0.0", "set-cookie-parser": "^3.0.0", "sirv": "^3.0.0" }, "peerDependencies": { "@opentelemetry/api": "^1.0.0", "@sveltejs/vite-plugin-svelte": "^3.0.0 || ^4.0.0-next.1 || ^5.0.0 || ^6.0.0-next.0 || ^7.0.0", "svelte": "^4.0.0 || ^5.0.0-next.0", "typescript": "^5.3.3 || ^6.0.0", "vite": "^5.0.3 || ^6.0.0 || ^7.0.0-beta.0 || ^8.0.0" }, "optionalPeers": ["@opentelemetry/api", "typescript"], "bin": { "svelte-kit": "svelte-kit.js" } }, "sha512-7nN4Ur4+nofZ36DVo83JbRe02m61Vc+I441mML/DYa1pUTZ/x26+lbrdqPen8gjmsUc6flMtHEqAtn0UfmfvAw=="],
 
     "@sveltejs/load-config": ["@sveltejs/load-config@0.1.1", "", {}, "sha512-BXXm+VOH/9X4N7Dd1iZ2MqA1h7M+9i2noI8QYuLDY8QcN2WHYn7D/VK/+IJNfcAmRw7ACNJ538UT9GXIhnBTiA=="],
 
@@ -264,7 +277,7 @@
 
     "devalue": ["devalue@5.8.1", "", {}, "sha512-4CXDYRBGqN+57wVJkuXBYmpAVUSg3L6JAQa/DFqm238G73E1wuyc/JhGQJzN7vUf/CMphYau2zXbfWzDR5aTEw=="],
 
-    "elysia": ["elysia@1.4.28", "", { "dependencies": { "cookie": "^1.1.1", "exact-mirror": "^0.2.7", "fast-decode-uri-component": "^1.0.1", "memoirist": "^0.4.0" }, "peerDependencies": { "@sinclair/typebox": ">= 0.34.0 < 1", "@types/bun": ">= 1.2.0", "file-type": ">= 20.0.0", "openapi-types": ">= 12.0.0", "typescript": ">= 5.0.0" }, "optionalPeers": ["@types/bun", "typescript"] }, "sha512-Vrx8sBnvq8squS/3yNBzR1jBXI+SgmnmvwawPjNuEHndUe5l1jV2Gp6JJ4ulDkEB8On6bWmmuyPpA+bq4t+WYg=="],
+    "elysia": ["elysia@1.4.29", "", { "dependencies": { "cookie": "^1.1.1", "exact-mirror": "^0.2.7", "fast-decode-uri-component": "^1.0.1", "memoirist": "^0.4.0" }, "peerDependencies": { "@sinclair/typebox": ">= 0.34.0 < 1", "@types/bun": ">= 1.2.0", "file-type": ">= 20.0.0", "openapi-types": ">= 12.0.0", "typescript": ">= 5.0.0" }, "optionalPeers": ["@types/bun", "typescript"] }, "sha512-GwMRGGwSdjfPt+w3LA0fqTuYJtS8uVRJicvoar98/HrO5qdFKDc9CwjIb6Kja+v39lkY+58hr2JvdR9jQzlUuA=="],
 
     "enhanced-resolve": ["enhanced-resolve@5.21.6", "", { "dependencies": { "graceful-fs": "^4.2.4", "tapable": "^2.3.3" } }, "sha512-aNnGCvbJ/RIyWo1IuhNdVjnNF+EjH9wpzpNHt+ci/m9He9LJvUN8wrCcXjp9cWsGNAuvSpVFTx/vraAFQ8qGjQ=="],
 
@@ -404,6 +417,8 @@
 
     "zipcodes-us": ["zipcodes-us@1.1.3", "", {}, "sha512-gOz8WAO6iWBU4aUc0lljpa+TKZckRKmgoHKcc1jWnn4eTbdc9XO5cXEaGccYn7GAjykueO0Wn+N7zdmzG0Uf5w=="],
 
+    "zod": ["zod@4.4.3", "", {}, "sha512-ytENFjIJFl2UwYglde2jchW2Hwm4GJFLDiSXWdTrJQBIN9Fcyp7n4DhxJEiWNAJMV1/BqWfW/kkg71UDcHJyTQ=="],
+
     "@sveltejs/kit/cookie": ["cookie@0.6.0", "", {}, "sha512-U71cyTamuh1CRNCfpGY6to28lxvNwPG4Guz/EVjgf3Jmzv0vlDp1atT9eS5dDjMYHucpHbWns6Lwf3BKz6svdw=="],
 
     "@tailwindcss/oxide-wasm32-wasi/@emnapi/core": ["@emnapi/core@1.11.1", "", { "dependencies": { "@emnapi/wasi-threads": "1.2.2", "tslib": "^2.4.0" }, "bundled": true }, "sha512-RSvbQmHzdKzNsLYa/wHrbc3KN4sYLKAdPZxqiM2HATqv/SBk2/ENSHpvXGaLOMcsAyz0poEGqkmmKYG3OWiJEQ=="],
diff --git a/packages/calculator/package.json b/packages/calculator/package.json
index 99db62f..e47fecc 100644
--- a/packages/calculator/package.json
+++ b/packages/calculator/package.json
@@ -4,7 +4,8 @@
     "version": "0.0.0",
     "type": "module",
     "dependencies": {
-        "ml-levenberg-marquardt": "^5.0.0"
+        "ml-levenberg-marquardt": "^5.0.0",
+        "@blade-and-brawn/domain": "workspace:*"
     },
     "exports": {
         ".": "./src/index.ts"
diff --git a/packages/calculator/src/avg-weights.ts b/packages/calculator/src/avg-weights.ts
new file mode 100644
index 0000000..e5843a9
--- /dev/null
+++ b/packages/calculator/src/avg-weights.ts
@@ -0,0 +1,30 @@
+import type { Gender, Metrics, StandardUnit } from "@blade-and-brawn/domain";
+import avgWeightDataJson from "./data/avg-weights.json" assert { type: "json" };
+
+export const getAvgWeight = (gender: Gender, age: number) => {
+    type AvgWeightData = {
+        metadata: {
+            unit: StandardUnit;
+        };
+        weights: Metrics[];
+    };
+    const avgWeightData = avgWeightDataJson as AvgWeightData;
+
+    const avgWeights = avgWeightData.weights.filter((a) => a.gender === gender);
+    const firstAvgWeight = avgWeights[0];
+    if (!firstAvgWeight) throw new Error("No average weights");
+
+    const closest = {
+        diff: Math.abs(firstAvgWeight.age - age),
+        avg: firstAvgWeight,
+    };
+    for (const avg of avgWeights) {
+        const diff = Math.abs(avg.age - age);
+        if (diff < closest.diff) {
+            closest.diff = diff;
+            closest.avg = avg;
+        }
+    }
+
+    return closest.avg.weight;
+};
diff --git a/packages/calculator/src/index.ts b/packages/calculator/src/index.ts
index 11a412f..0515eb1 100644
--- a/packages/calculator/src/index.ts
+++ b/packages/calculator/src/index.ts
@@ -2,17 +2,18 @@ import {
     Activity,
     Attribute,
     Gender,
-    getAvgWeight,
     kgToLb,
     lbToKg,
     range,
+    type Metrics,
     type ActivityPerformance,
     type Player,
     type StandardUnit,
-} from "../src/util";
+} from "@blade-and-brawn/domain";
 import { levenbergMarquardt as LM } from "ml-levenberg-marquardt";
 import defaultConfig from "./config.json" assert { type: "json" };
 import defaultStandardsJson from "./data/default-standards.json" assert { type: "json" };
+import { getAvgWeight } from "./avg-weights";
 
 // SOURCES
 // Squat, Bench, Dead Lift:
@@ -24,8 +25,6 @@ import defaultStandardsJson from "./data/default-standards.json" assert { type:
 // 3 Cone drill:
 // https://nflsavant.com/combine.php?utm_source=chatgpt.com
 
-export * from "./util";
-
 export type LevelCalculatorOutput = {
     player: number;
     attributes: Record<Attribute, number>;
@@ -33,12 +32,6 @@ export type LevelCalculatorOutput = {
 
 export type Levels = Record<string, number>;
 
-export interface Metrics {
-    age: number;
-    weight: number;
-    gender: Gender;
-}
-
 type NumberMetric = Extract<keyof Metrics, "age" | "weight">;
 
 export interface Standard {
@@ -72,7 +65,7 @@ const metricPriority = (m: NumberMetric) => {
 export const DEFAULT_STANDARDS_DATA = defaultStandardsJson as StandardsData;
 
 export class LevelCalculator {
-    standards: Standards;
+    readonly standards: Standards;
 
     public constructor(standards: Standards) {
         this.standards = standards;
@@ -191,7 +184,7 @@ export class LevelCalculator {
 
         const activityLevelsAvg = Math.round(
             activityLevels.reduce((sum, curr) => sum + curr, 0) /
-                activityLevels.length,
+            activityLevels.length,
         );
 
         return activityLevelsAvg;
@@ -392,9 +385,9 @@ export class Standards {
             // generate data
             const allGenerators = this.cfg.activity[activity].enableGeneration
                 ? this.standardsData[activity].metadata.generators.sort(
-                      (a, b) =>
-                          metricPriority(a.metric) - metricPriority(b.metric),
-                  )
+                    (a, b) =>
+                        metricPriority(a.metric) - metricPriority(b.metric),
+                )
                 : [];
 
             for (const generator of allGenerators) {
@@ -664,7 +657,7 @@ export class Standards {
                     weightUpper === weightLower
                         ? 1
                         : (metrics.weight - weightLower) /
-                          (weightUpper - weightLower);
+                        (weightUpper - weightLower);
                 weightRatio = Math.max(0, Math.min(1, weightRatio));
 
                 // metrics.weight = lowerAgeWeightStandard.metrics.weight + (upperAgeWeightStandard.metrics.weight - lowerAgeWeightStandard.metrics.weight) * weightRatio;
diff --git a/packages/calculator/src/util.ts b/packages/calculator/src/util.ts
deleted file mode 100644
index 93f27d2..0000000
--- a/packages/calculator/src/util.ts
+++ /dev/null
@@ -1,100 +0,0 @@
-import { type Metrics } from ".";
-import avgWeightDataRaw from "./data/avg-weights.json";
-
-// -------------------------------------------------------------------------------------------------
-// DATA MODELS
-// -------------------------------------------------------------------------------------------------
-
-export type Player = {
-    name?: string;
-    metrics: Metrics;
-};
-
-export enum Attribute {
-    Strength = "Strength",
-    Power = "Power",
-    Endurance = "Endurance",
-    Agility = "Agility",
-}
-
-export enum Activity {
-    BackSquat = "BackSquat",
-    Deadlift = "Deadlift",
-    BenchPress = "BenchPress",
-    Run = "Run",
-    BroadJump = "BroadJump",
-    ConeDrill = "ConeDrill",
-}
-
-export interface ActivityPerformance {
-    activity: Activity;
-    performance: number;
-}
-
-export enum Gender {
-    Male = "Male",
-    Female = "Female",
-}
-
-// -------------------------------------------------------------------------------------------------
-// Conversion utilities
-// -------------------------------------------------------------------------------------------------
-
-export type StandardUnit = "ms" | "cm" | "kg";
-
-export const lbToKg = (lb: number | string): number => +lb * 0.453592;
-export const kgToLb = (kg: number | string): number => +kg * 2.20462;
-
-export const minToMs = (min: number) => min * 60000;
-export const secToMs = (sec: number) => sec * 1000;
-export const msToMin = (ms: number) => ms / 60000;
-
-export const ftToCm = (ft: number) => ft * 30.48;
-export const inToCm = (inches: number) => inches * 2.54;
-export const cmToIn = (cm: number) => cm / 2.54;
-
-export const msToTime = (ms: number, includeMs = false): string => {
-    const minutes = Math.floor(ms / 60000);
-    const seconds = Math.floor((ms % 60000) / 1000);
-    const milliseconds = Math.floor(ms % 1000);
-
-    let formattedTime = `${minutes}:${seconds.toString().padStart(2, "0")}`;
-    if (includeMs) {
-        formattedTime += `.${milliseconds.toString().padStart(3, "0")}`;
-    }
-    return formattedTime;
-};
-
-export const range = (length: number) =>
-    Array.from({ length: length }, (_, i) => i);
-
-export const clamp = (x: number, lo: number, hi: number) =>
-    Math.max(lo, Math.min(hi, x));
-
-export const getAvgWeight = (gender: Gender, age: number) => {
-    type AvgWeightData = {
-        metadata: {
-            unit: StandardUnit;
-        };
-        weights: Metrics[];
-    };
-    let avgWeightData = avgWeightDataRaw as AvgWeightData;
-
-    const avgWeights = avgWeightData.weights.filter((a) => a.gender === gender);
-    const firstAvgWeight = avgWeights[0];
-    if (!firstAvgWeight) throw new Error("No average weights");
-
-    const closest = {
-        diff: Math.abs(firstAvgWeight.age - age),
-        avg: firstAvgWeight,
-    };
-    for (const avg of avgWeights) {
-        const diff = Math.abs(avg.age - age);
-        if (diff < closest.diff) {
-            closest.diff = diff;
-            closest.avg = avg;
-        }
-    }
-
-    return closest.avg.weight;
-};
diff --git a/packages/commerce/src/sync.ts b/packages/commerce/src/sync.ts
index 5f25d50..4054e15 100644
--- a/packages/commerce/src/sync.ts
+++ b/packages/commerce/src/sync.ts
@@ -24,7 +24,7 @@ export class SyncService {
         syncingIds: [] as number[],
     };
 
-    static async sync(printfulProductId: number | undefined) {
+    static async sync(printfulProductId?: number) {
         this.state.isSyncing = true;
 
         // Populate products
diff --git a/packages/domain/package.json b/packages/domain/package.json
new file mode 100644
index 0000000..b90917b
--- /dev/null
+++ b/packages/domain/package.json
@@ -0,0 +1,13 @@
+{
+    "name": "@blade-and-brawn/domain",
+    "private": true,
+    "version": "0.0.0",
+    "type": "module",
+    "dependencies": {
+        "@blade-and-brawn/domain": "workspace:*",
+        "zod": "^4.4.3"
+    },
+    "exports": {
+        ".": "./src/index.ts"
+    }
+}
diff --git a/packages/domain/src/index.ts b/packages/domain/src/index.ts
new file mode 100644
index 0000000..88b41fe
--- /dev/null
+++ b/packages/domain/src/index.ts
@@ -0,0 +1,2 @@
+export * from "./models"
+export * from "./utils"
diff --git a/packages/domain/src/models.ts b/packages/domain/src/models.ts
new file mode 100644
index 0000000..026b447
--- /dev/null
+++ b/packages/domain/src/models.ts
@@ -0,0 +1,44 @@
+import { z } from "zod";
+
+export enum Attribute {
+    Strength = "Strength",
+    Power = "Power",
+    Endurance = "Endurance",
+    Agility = "Agility",
+}
+
+export enum Activity {
+    BackSquat = "BackSquat",
+    Deadlift = "Deadlift",
+    BenchPress = "BenchPress",
+    Run = "Run",
+    BroadJump = "BroadJump",
+    ConeDrill = "ConeDrill",
+}
+
+export enum Gender {
+    Male = "Male",
+    Female = "Female",
+}
+
+export const MetricsSchema = z.object({
+    age: z.number(),
+    weight: z.number(),
+    gender: z.enum(Gender),
+});
+
+export const PlayerSchema = z.object({
+    name: z.string().optional(),
+    metrics: MetricsSchema,
+});
+
+export const ActivityPerformanceSchema = z.object({
+    activity: z.enum(Activity),
+    performance: z.number(),
+});
+
+export type StandardUnit = "ms" | "cm" | "kg";
+
+export type Metrics = z.infer<typeof MetricsSchema>;
+export type Player = z.infer<typeof PlayerSchema>;
+export type ActivityPerformance = z.infer<typeof ActivityPerformanceSchema>;
diff --git a/packages/domain/src/utils.ts b/packages/domain/src/utils.ts
new file mode 100644
index 0000000..6c6d256
--- /dev/null
+++ b/packages/domain/src/utils.ts
@@ -0,0 +1,28 @@
+export const lbToKg = (lb: number | string): number => +lb * 0.453592;
+export const kgToLb = (kg: number | string): number => +kg * 2.20462;
+
+export const minToMs = (min: number) => min * 60000;
+export const secToMs = (sec: number) => sec * 1000;
+export const msToMin = (ms: number) => ms / 60000;
+
+export const ftToCm = (ft: number) => ft * 30.48;
+export const inToCm = (inches: number) => inches * 2.54;
+export const cmToIn = (cm: number) => cm / 2.54;
+
+export const msToTime = (ms: number, includeMs = false): string => {
+    const minutes = Math.floor(ms / 60000);
+    const seconds = Math.floor((ms % 60000) / 1000);
+    const milliseconds = Math.floor(ms % 1000);
+
+    let formattedTime = `${minutes}:${seconds.toString().padStart(2, "0")}`;
+    if (includeMs) {
+        formattedTime += `.${milliseconds.toString().padStart(3, "0")}`;
+    }
+    return formattedTime;
+};
+
+export const range = (length: number) =>
+    Array.from({ length: length }, (_, i) => i);
+
+export const clamp = (x: number, lo: number, hi: number) =>
+    Math.max(lo, Math.min(hi, x));