diff --git a/projects/using-ide-features/typearium/01-favorite-animals/README.md b/projects/using-ide-features/typearium/01-favorite-animals/README.md
new file mode 100644
index 00000000..9c062f55
--- /dev/null
+++ b/projects/using-ide-features/typearium/01-favorite-animals/README.md
@@ -0,0 +1,13 @@
+# Step 1: Favorite Animals
+
+We keep track of our visitors' favorite animals by a combination of informal polling and park ticket data.
+The program we use to work with that data stores that list of favorites as an array of strings... duplicated in multiple places.
+We have to modify all those places whenever the list needs updating.
+
+Could you please use your IDE to extract the array into a shared constant, and re-use that constant?
+
+## Files
+
+- `index.ts`: Refactor the functions here
+- `index.test.ts`: Tests verifying the refactored functions
+- `solution.ts`: Solution code
diff --git a/projects/using-ide-features/typearium/01-favorite-animals/index.test.ts b/projects/using-ide-features/typearium/01-favorite-animals/index.test.ts
new file mode 100644
index 00000000..b6710490
--- /dev/null
+++ b/projects/using-ide-features/typearium/01-favorite-animals/index.test.ts
@@ -0,0 +1,57 @@
+import { describe, expect, it } from "@jest/globals";
+
+import * as index from "./index";
+import * as solution from "./solution";
+
+const { checkIsAnyAnimalFavorite, getFavoriteAnimals, logFavoriteAnimals } =
+	process.env.TEST_SOLUTIONS ? solution : index;
+
+describe(checkIsAnyAnimalFavorite, () => {
+	it("returns true for a favorite animal", () => {
+		expect(checkIsAnyAnimalFavorite("parakeet")).toBe(true);
+	});
+
+	it("returns true for a favorite animal then a non-favorite animal", () => {
+		expect(checkIsAnyAnimalFavorite("parakeet", "snake")).toBe(true);
+	});
+
+	it("returns true for a non-favorite animal then a favorite animal", () => {
+		expect(checkIsAnyAnimalFavorite("snake", "parakeet")).toBe(true);
+	});
+
+	it("returns false for a non-favorite animal", () => {
+		expect(checkIsAnyAnimalFavorite("snake")).toBe(false);
+	});
+
+	it("does not include its own list of animals", () => {
+		expect(checkIsAnyAnimalFavorite.toString()).not.toMatch(/parakeet/);
+	});
+});
+
+describe(getFavoriteAnimals, () => {
+	it("returns all favorite animals by default", () => {
+		expect(getFavoriteAnimals()).toEqual([
+			"parakeet",
+			"macaw",
+			"cat",
+			"monkey",
+			"elephant",
+			"alpaca",
+			"fox",
+		]);
+	});
+
+	it("returns a limited quantity of favorite animals when a quantity is provided", () => {
+		expect(getFavoriteAnimals(3)).toEqual(["parakeet", "macaw", "cat"]);
+	});
+
+	it("does not include its own list of animals", () => {
+		expect(getFavoriteAnimals.toString()).not.toMatch(/parakeet/);
+	});
+});
+
+describe(logFavoriteAnimals, () => {
+	it("does not include its own list of animals", () => {
+		expect(logFavoriteAnimals.toString()).not.toMatch(/parakeet/);
+	});
+});
diff --git a/projects/using-ide-features/typearium/01-favorite-animals/index.ts b/projects/using-ide-features/typearium/01-favorite-animals/index.ts
new file mode 100644
index 00000000..e5beb06a
--- /dev/null
+++ b/projects/using-ide-features/typearium/01-favorite-animals/index.ts
@@ -0,0 +1,35 @@
+// Refactor here! ✨
+
+export function checkIsAnyAnimalFavorite(...animals: string[]) {
+	const favoriteAnimalsUnique = new Set([
+		"parakeet",
+		"macaw",
+		"cat",
+		"monkey",
+		"elephant",
+		"alpaca",
+		"fox",
+	]);
+
+	return animals.some((animal) => favoriteAnimalsUnique.has(animal));
+}
+
+export function getFavoriteAnimals(max = Infinity) {
+	return [
+		"parakeet",
+		"macaw",
+		"cat",
+		"monkey",
+		"elephant",
+		"alpaca",
+		"fox",
+	].slice(0, max);
+}
+
+export function logFavoriteAnimals() {
+	["parakeet", "macaw", "cat", "monkey", "elephant", "alpaca", "fox"].forEach(
+		(animal, i) => {
+			console.log(`I like ${animal} number ${i}!`);
+		}
+	);
+}
diff --git a/projects/using-ide-features/typearium/01-favorite-animals/solution.ts b/projects/using-ide-features/typearium/01-favorite-animals/solution.ts
new file mode 100644
index 00000000..d15470e6
--- /dev/null
+++ b/projects/using-ide-features/typearium/01-favorite-animals/solution.ts
@@ -0,0 +1,27 @@
+// Refactor here! ✨
+
+const favoriteAnimals = [
+	"parakeet",
+	"macaw",
+	"cat",
+	"monkey",
+	"elephant",
+	"alpaca",
+	"fox",
+];
+
+export function checkIsAnyAnimalFavorite(...animals: string[]) {
+	const favoriteAnimalsUnique = new Set(favoriteAnimals);
+
+	return animals.some((animal) => favoriteAnimalsUnique.has(animal));
+}
+
+export function getFavoriteAnimals(quantity = Infinity) {
+	return favoriteAnimals.slice(0, quantity);
+}
+
+export function logFavoriteAnimals() {
+	favoriteAnimals.forEach((animal, i) => {
+		console.log(`I like ${animal} number ${i}!`);
+	});
+}
diff --git a/projects/using-ide-features/typearium/02-species-collections/README.md b/projects/using-ide-features/typearium/02-species-collections/README.md
new file mode 100644
index 00000000..c0afd822
--- /dev/null
+++ b/projects/using-ide-features/typearium/02-species-collections/README.md
@@ -0,0 +1,24 @@
+# Step 2: Species Collections
+
+Lovely, now we can log our favorite animals much more easily!
+Thank you!
+
+...
+
+right click to move to new file
+
+add nesting for fauna/\*, flora/\*
+
+typescript names the files like "MammalsSettings.ts" - change name to just "fauna/mammals.ts"
+
+...
+
+:::tip
+once you're done, use find-all-references on `onlyTruthy` and the various settings interfaces to practice navigating with IDE features.
+:::
+
+## Files
+
+- `index.ts`: Refactor the functions here
+- `index.test.ts`: Tests verifying the refactored functions
+- `solution.ts`: Solution code
diff --git a/projects/using-ide-features/typearium/02-species-collections/fauna.solution.ts b/projects/using-ide-features/typearium/02-species-collections/fauna.solution.ts
new file mode 100644
index 00000000..91560219
--- /dev/null
+++ b/projects/using-ide-features/typearium/02-species-collections/fauna.solution.ts
@@ -0,0 +1,11 @@
+import { getMammals, MammalsSettings } from "./fauna/mammals.solution";
+import { getReptiles, ReptilesSettings } from "./fauna/reptiles.solution";
+
+export interface FaunaSettings {
+	mammals?: MammalsSettings;
+	reptiles?: ReptilesSettings;
+}
+
+export function getFauna(settings?: FaunaSettings) {
+	return [getMammals(settings?.mammals), getReptiles(settings?.reptiles)];
+}
diff --git a/projects/using-ide-features/typearium/02-species-collections/fauna/mammals.solution.ts b/projects/using-ide-features/typearium/02-species-collections/fauna/mammals.solution.ts
new file mode 100644
index 00000000..db22f5c3
--- /dev/null
+++ b/projects/using-ide-features/typearium/02-species-collections/fauna/mammals.solution.ts
@@ -0,0 +1,17 @@
+import { onlyTruthy } from "../utils/onlyTruthy.solution";
+
+export interface MammalsSettings {
+	cute?: boolean;
+	deadly?: boolean;
+}
+
+export function getMammals(settings?: MammalsSettings) {
+	return onlyTruthy(
+		settings?.cute && [
+			"cats",
+			"dogs",
+			settings?.deadly && "monty python rabbit",
+		],
+		settings?.deadly && ["lion", "tiger"]
+	);
+}
diff --git a/projects/using-ide-features/typearium/02-species-collections/fauna/reptiles.solution.ts b/projects/using-ide-features/typearium/02-species-collections/fauna/reptiles.solution.ts
new file mode 100644
index 00000000..4c29c56b
--- /dev/null
+++ b/projects/using-ide-features/typearium/02-species-collections/fauna/reptiles.solution.ts
@@ -0,0 +1,13 @@
+import { onlyTruthy } from "../utils/onlyTruthy.solution";
+
+export interface ReptilesSettings {
+	ferocious?: boolean;
+	small?: boolean;
+}
+
+export function getReptiles(settings?: ReptilesSettings) {
+	return onlyTruthy(
+		settings?.ferocious && "dragon",
+		settings?.small && ["frog", "gecko"]
+	);
+}
diff --git a/projects/using-ide-features/typearium/02-species-collections/flora.solution.ts b/projects/using-ide-features/typearium/02-species-collections/flora.solution.ts
new file mode 100644
index 00000000..2dc403d8
--- /dev/null
+++ b/projects/using-ide-features/typearium/02-species-collections/flora.solution.ts
@@ -0,0 +1,11 @@
+import { FlowersSettings, getFlowers } from "./flora/flowers.solution";
+import { TreesSettings, getTrees } from "./flora/trees.solution";
+
+export interface FloraSettings {
+	flowers?: FlowersSettings;
+	trees?: TreesSettings;
+}
+
+export function getFlora(settings?: FloraSettings) {
+	return [getFlowers(settings?.flowers), getTrees(settings?.trees)];
+}
diff --git a/projects/using-ide-features/typearium/02-species-collections/flora/flowers.solution.ts b/projects/using-ide-features/typearium/02-species-collections/flora/flowers.solution.ts
new file mode 100644
index 00000000..4f65a71e
--- /dev/null
+++ b/projects/using-ide-features/typearium/02-species-collections/flora/flowers.solution.ts
@@ -0,0 +1,13 @@
+import { onlyTruthy } from "../utils/onlyTruthy.solution";
+
+export interface FlowersSettings {
+	colorful?: boolean;
+	prickly?: boolean;
+}
+
+export function getFlowers(settings?: FlowersSettings) {
+	return onlyTruthy(
+		settings?.colorful && ["carnation", "lilac", "tulip"],
+		settings?.colorful && settings?.prickly && "rose"
+	);
+}
diff --git a/projects/using-ide-features/typearium/02-species-collections/flora/trees.solution.ts b/projects/using-ide-features/typearium/02-species-collections/flora/trees.solution.ts
new file mode 100644
index 00000000..26ca2967
--- /dev/null
+++ b/projects/using-ide-features/typearium/02-species-collections/flora/trees.solution.ts
@@ -0,0 +1,13 @@
+import { onlyTruthy } from "../utils/onlyTruthy.solution";
+
+export interface TreesSettings {
+	evergreen?: boolean;
+	fruitBearing?: boolean;
+}
+
+export function getTrees(settings?: TreesSettings) {
+	return onlyTruthy(
+		settings?.evergreen && "pine",
+		settings?.fruitBearing && ["apple", "pear"]
+	);
+}
diff --git a/projects/using-ide-features/typearium/02-species-collections/index.solution.ts b/projects/using-ide-features/typearium/02-species-collections/index.solution.ts
new file mode 100644
index 00000000..58f4137c
--- /dev/null
+++ b/projects/using-ide-features/typearium/02-species-collections/index.solution.ts
@@ -0,0 +1,14 @@
+// Refactor here! ✨
+
+import { FaunaSettings, getFauna } from "./fauna.solution";
+import { FloraSettings, getFlora } from "./flora.solution";
+import { onlyTruthy } from "./utils/onlyTruthy.solution";
+
+export interface EverythingSettings {
+	fauna?: FaunaSettings;
+	flora?: FloraSettings;
+}
+
+export function getEverything(settings?: EverythingSettings) {
+	return onlyTruthy(getFauna(settings?.fauna), getFlora(settings?.flora));
+}
diff --git a/projects/using-ide-features/typearium/02-species-collections/index.test.ts b/projects/using-ide-features/typearium/02-species-collections/index.test.ts
new file mode 100644
index 00000000..b99ccf33
--- /dev/null
+++ b/projects/using-ide-features/typearium/02-species-collections/index.test.ts
@@ -0,0 +1,60 @@
+import { describe, expect, it, test } from "@jest/globals";
+
+import * as index from "./index";
+import * as solution from "./index.solution";
+
+const { getEverything } = process.env.TEST_SOLUTIONS ? solution : index;
+
+describe(getEverything, () => {
+	it("returns nothing with no settings", () => {
+		expect(getEverything()).toMatchInlineSnapshot(`Array []`);
+	});
+
+	it("returns everything with all settings", () => {
+		expect(
+			getEverything({
+				fauna: {
+					mammals: {
+						cute: true,
+						deadly: true,
+					},
+
+					reptiles: {
+						ferocious: true,
+						small: true,
+					},
+				},
+
+				flora: {
+					flowers: {
+						colorful: true,
+						prickly: true,
+					},
+
+					trees: {
+						evergreen: true,
+						fruitBearing: true,
+					},
+				},
+			})
+		).toMatchInlineSnapshot(`
+		Array [
+		  "cats",
+		  "dogs",
+		  "monty python rabbit",
+		  "lion",
+		  "tiger",
+		  "dragon",
+		  "frog",
+		  "gecko",
+		  "carnation",
+		  "lilac",
+		  "tulip",
+		  "rose",
+		  "pine",
+		  "apple",
+		  "pear",
+		]
+	`);
+	});
+});
diff --git a/projects/using-ide-features/typearium/02-species-collections/index.ts b/projects/using-ide-features/typearium/02-species-collections/index.ts
new file mode 100644
index 00000000..00af396e
--- /dev/null
+++ b/projects/using-ide-features/typearium/02-species-collections/index.ts
@@ -0,0 +1,100 @@
+// Refactor here! ✨
+
+export type DeepStringsMaybe =
+	| string
+	| boolean
+	| undefined
+	| DeepStringsMaybe[];
+
+function onlyTruthy(...items: DeepStringsMaybe[]): string[] {
+	return items.flatMap((item) => {
+		if (typeof item === "string") {
+			return item;
+		}
+
+		if (item instanceof Array) {
+			return item.flatMap((subItem) => onlyTruthy(subItem));
+		}
+
+		return [];
+	});
+}
+
+interface MammalsSettings {
+	cute?: boolean;
+	deadly?: boolean;
+}
+
+function getMammals(settings?: MammalsSettings) {
+	return onlyTruthy(
+		settings?.cute && [
+			"cats",
+			"dogs",
+			settings?.deadly && "monty python rabbit",
+		],
+		settings?.deadly && ["lion", "tiger"]
+	);
+}
+
+interface ReptilesSettings {
+	ferocious?: boolean;
+	small?: boolean;
+}
+
+function getReptiles(settings?: ReptilesSettings) {
+	return onlyTruthy(
+		settings?.ferocious && "dragon",
+		settings?.small && ["frog", "gecko"]
+	);
+}
+
+interface FaunaSettings {
+	mammals?: MammalsSettings;
+	reptiles?: ReptilesSettings;
+}
+
+function getFauna(settings?: FaunaSettings) {
+	return [getMammals(settings?.mammals), getReptiles(settings?.reptiles)];
+}
+
+interface FlowersSettings {
+	colorful?: boolean;
+	prickly?: boolean;
+}
+
+function getFlowers(settings?: FlowersSettings) {
+	return onlyTruthy(
+		settings?.colorful && ["carnation", "lilac", "tulip"],
+		settings?.colorful && settings?.prickly && "rose"
+	);
+}
+
+interface TreesSettings {
+	evergreen?: boolean;
+	fruitBearing?: boolean;
+}
+
+function getTrees(settings?: TreesSettings) {
+	return onlyTruthy(
+		settings?.evergreen && "pine",
+		settings?.fruitBearing && ["apple", "pear"]
+	);
+}
+
+interface FloraSettings {
+	flowers?: FlowersSettings;
+	trees?: TreesSettings;
+}
+
+function getFlora(settings?: FloraSettings) {
+	return [getFlowers(settings?.flowers), getTrees(settings?.trees)];
+}
+
+export interface EverythingSettings {
+	fauna?: FaunaSettings;
+	flora?: FloraSettings;
+}
+
+export function getEverything(settings?: EverythingSettings) {
+	return onlyTruthy(getFauna(settings?.fauna), getFlora(settings?.flora));
+}
diff --git a/projects/using-ide-features/typearium/02-species-collections/utils/onlyTruthy.solution.ts b/projects/using-ide-features/typearium/02-species-collections/utils/onlyTruthy.solution.ts
new file mode 100644
index 00000000..5a83288d
--- /dev/null
+++ b/projects/using-ide-features/typearium/02-species-collections/utils/onlyTruthy.solution.ts
@@ -0,0 +1,19 @@
+export type DeepStringsMaybe =
+	| string
+	| boolean
+	| undefined
+	| DeepStringsMaybe[];
+
+export function onlyTruthy(...items: DeepStringsMaybe[]): string[] {
+	return items.flatMap((item) => {
+		if (typeof item === "string") {
+			return item;
+		}
+
+		if (item instanceof Array) {
+			return item.flatMap((subItem) => onlyTruthy(subItem));
+		}
+
+		return [];
+	});
+}
diff --git a/projects/using-ide-features/typearium/README.md b/projects/using-ide-features/typearium/README.md
new file mode 100644
index 00000000..bba10076
--- /dev/null
+++ b/projects/using-ide-features/typearium/README.md
@@ -0,0 +1,34 @@
+# Typearium
+
+> A [Learning TypeScript > Using IDE Features](https://learning-typescript.com/using-ide-features) 🥗 appetizer project.
+
+Welcome to the Typearium: a combination acquarium/terrarium/vivarium that keeps animals in the form of TypeScript types.
+We're quite niche.
+
+Because we're so niche, we haven't had the budget to invest in updating our (somewhat legacy) code.
+It's a good thing we originally wrote it in TypeScript, because we're hoping you can use IDE features powered by TypeScript to help with some refactors!
+
+## Setup
+
+In one terminal, start the TypeScript compiler in watch mode:
+
+```shell
+tsc --watch
+```
+
+In another terminal, run Jest on whichever step you're working on.
+For example, to run tests for the first step in watch mode:
+
+```shell
+npm test -- 1 --watch
+```
+
+## Steps
+
+- [1. Favorite Animals](./01-favorite-animals)
+- [2. Species Trees](./02-species-trees)
+
+## Notes
+
+- Remember, this is meant to exercise your IDE refactoring skills.
+- Don't import code from one step into another.
diff --git a/projects/using-ide-features/typearium/_category_.json b/projects/using-ide-features/typearium/_category_.json
new file mode 100644
index 00000000..ed4e395c
--- /dev/null
+++ b/projects/using-ide-features/typearium/_category_.json
@@ -0,0 +1,4 @@
+{
+	"label": "🥗 Typearium",
+	"position": 1
+}
diff --git a/projects/using-ide-features/typearium/jest.config.js b/projects/using-ide-features/typearium/jest.config.js
new file mode 100644
index 00000000..0bcb2272
--- /dev/null
+++ b/projects/using-ide-features/typearium/jest.config.js
@@ -0,0 +1,12 @@
+module.exports = {
+	transform: {
+		"^.+\\.(t|j)sx?$": [
+			"@swc/jest",
+			{
+				jsc: {
+					target: "es2021",
+				},
+			},
+		],
+	},
+};
diff --git a/projects/using-ide-features/typearium/package.json b/projects/using-ide-features/typearium/package.json
new file mode 100644
index 00000000..9e928345
--- /dev/null
+++ b/projects/using-ide-features/typearium/package.json
@@ -0,0 +1,7 @@
+{
+	"name": "analyzing-dna",
+	"scripts": {
+		"test": "jest",
+		"test:solutions": "cross-env TEST_SOLUTIONS=1 jest"
+	}
+}