diff --git a/src/components/apps/calculator/Calculator.jsx b/src/components/apps/calculator/Calculator.jsx
index 0ef4897..60da984 100644
--- a/src/components/apps/calculator/Calculator.jsx
+++ b/src/components/apps/calculator/Calculator.jsx
@@ -1,7 +1,207 @@
-// import styles from "./Calculator.module.css";
+import { useCallback, useEffect, useState } from "react";
+import { Button } from "../../_utils/button/Button.jsx";
+import styles from "./Calculator.module.css";
 
-export function Calculator() {
-	return (
-		<div></div>
-	);
+/** @type {import("../../windows/WindowView.jsx").windowProps} */
+export function Calculator({ active }) {
+	const [input, setInput] = useState("0");
+	const [firstNumber, setFirstNumber] = useState(null);
+	const [secondNumber, setSecondNumber] = useState(null);
+	const [operation, setOperation] = useState(null);
+	const [isIntermediate, setIsIntermediate] = useState(false);
+
+	const log = useCallback(() => {
+		console.info({ input, firstNumber, secondNumber, operation });
+	}, [firstNumber, input, operation, secondNumber]);
+
+	const reset = useCallback(() => {
+		setInput("0");
+		setFirstNumber(null);
+		setSecondNumber(null);
+		setOperation(null);
+
+		log();
+	}, [log]);
+
+	const addInput = useCallback((string) => {
+		let hasReset = false;
+		if (secondNumber != null) {
+			if (isIntermediate) {
+				setFirstNumber(input);
+				setSecondNumber(null);
+				setInput(null);
+			} else {
+				reset();
+			}
+			hasReset = true;
+		}			
+
+		if (string === "." && input?.includes("."))
+			return;
+
+		if (string === "-") {
+			if (input === "0") {
+				setInput("-0");
+			} else {
+				setInput((parseFloat(input) * -1).toString());
+			}
+		} else if (string === "%") {
+			setInput((parseFloat(input) / 100).toString());
+		} else if (input === "0" || input === "-0" || input == null || hasReset) {
+			if (string === ".") {
+				setInput(input === "-0" ? "0." : "0.");
+			} else {
+				setInput(input === "-0" ? `-${string}` : string);
+			}
+		} else {
+			setInput(input + string);
+		}
+
+		log();
+	}, [input, isIntermediate, log, reset, secondNumber]);
+
+	const calculate = useCallback((intermediate = false) => {
+		if (firstNumber == null) {
+
+		} else {
+			setSecondNumber(input);
+
+			const a = parseFloat(firstNumber);
+			const b = parseFloat(input);
+			
+			let result = 0;
+			switch (operation) {
+				case "×":
+					result = a * b;
+					break;
+				case "÷":
+					result = a / b;
+					break;
+				case "+":
+					result = a + b;
+					break;
+				case "-":
+					result = a - b;
+					break;
+			}
+
+			setInput(result.toString());
+		}
+
+		setIsIntermediate(intermediate);
+
+		log();
+	}, [firstNumber, input, log, operation]);
+
+	const changeOperation = useCallback((operation) => {
+		if (firstNumber != null && secondNumber == null) {
+			calculate(true);
+		} else {
+			setFirstNumber(input);
+			setSecondNumber(null);
+			setInput(null);
+		}
+
+		setOperation(operation);
+
+		log();
+	}, [calculate, firstNumber, input, log, secondNumber]);
+
+	useEffect(() => {
+		const onKeyDown = (event) => {
+			if (!active)
+				return;
+
+			console.log(event.key);
+
+			event.preventDefault();
+
+			switch (event.key) {
+				case "0":
+				case "1":
+				case "2":
+				case "3":
+				case "4":
+				case "5":
+				case "6":
+				case "7":
+				case "8":
+				case "9":
+					addInput(event.key);
+					break;
+				case ".":
+				case ",":
+					addInput(".");
+					break;
+				case "Escape":
+					reset();
+					break;
+				case "=":
+				case "Enter":
+					calculate();
+					break;
+				case "*":
+					changeOperation("×");
+					break;
+				case "/":
+					changeOperation("÷");
+					break;
+				case "+":
+				case "-":
+					changeOperation(event.key);
+					break;
+				case "%":
+					addInput("%");
+					break;
+			}
+		};
+
+		document.addEventListener("keydown", onKeyDown);
+
+		return () => {
+			document.removeEventListener("keydown", onKeyDown);
+		};
+	}, [active, addInput, calculate, changeOperation, reset]);
+
+	let calculation = "";
+	if (operation != null)
+		calculation = `${firstNumber} ${operation} ${secondNumber != null ? secondNumber + " =" : ""}`;
+
+	return (<div className={styles.Container}>
+		<div className={styles.Output}>
+			<p className={styles.Calculation}>{calculation}</p>
+			<p className={styles.Preview}>{input ?? firstNumber}</p>
+		</div>
+		<div className={styles.Input}>
+			<div className={styles["Input-row"]}>
+				<Button className={styles.Button} onClick={reset}>C</Button>
+				<Button className={styles.Button} onClick={() => { addInput("-"); }}>+/-</Button>
+				<Button className={styles.Button} onClick={() => { addInput("%"); }}>%</Button>
+				<Button className={styles.Button} onClick={() => { changeOperation("÷"); }}>÷</Button>
+			</div>
+			<div className={styles["Input-row"]}>
+				<Button className={styles.Button} onClick={() => { addInput("7"); }}>7</Button>
+				<Button className={styles.Button} onClick={() => { addInput("8"); }}>8</Button>
+				<Button className={styles.Button} onClick={() => { addInput("9"); }}>9</Button>
+				<Button className={styles.Button} onClick={() => { changeOperation("×"); }}>×</Button>
+			</div>
+			<div className={styles["Input-row"]}>
+				<Button className={styles.Button} onClick={() => { addInput("4"); }}>4</Button>
+				<Button className={styles.Button} onClick={() => { addInput("5"); }}>5</Button>
+				<Button className={styles.Button} onClick={() => { addInput("6"); }}>6</Button>
+				<Button className={styles.Button} onClick={() => { changeOperation("-"); }}>-</Button>
+			</div>
+			<div className={styles["Input-row"]}>
+				<Button className={styles.Button} onClick={() => { addInput("1"); }}>1</Button>
+				<Button className={styles.Button} onClick={() => { addInput("2"); }}>2</Button>
+				<Button className={styles.Button} onClick={() => { addInput("3"); }}>3</Button>
+				<Button className={styles.Button} onClick={() => { changeOperation("+"); }}>+</Button>
+			</div>
+			<div className={styles["Input-row"]}>
+				<Button className={`${styles.Button} ${styles["Button-large"]}`} onClick={() => { addInput("0"); }}>0</Button>
+				<Button className={styles.Button} onClick={() => { addInput("."); }}>.</Button>
+				<Button className={styles.Button} onClick={() => { calculate(); }}>=</Button>
+			</div>
+		</div>
+	</div>);
 }
\ No newline at end of file
diff --git a/src/components/apps/calculator/Calculator.module.css b/src/components/apps/calculator/Calculator.module.css
index e69de29..c603b11 100644
--- a/src/components/apps/calculator/Calculator.module.css
+++ b/src/components/apps/calculator/Calculator.module.css
@@ -0,0 +1,67 @@
+.Container {
+	display: flex;
+	flex-direction: column;
+	height: 100%;
+
+	--output-height: 20%;
+	--button-gap: 0.25rem;
+}
+
+.Output {
+	display: flex;
+	gap: 0.25rem;
+	flex-direction: column;
+	justify-content: center;
+	align-items: flex-end;
+	height: var(--output-height);
+	padding: 0.5rem;
+}
+
+.Calculation, .Preview {
+	margin: 0;
+}
+
+.Calculation {
+	color: var(--foreground-color-c);
+	height: 1.25rem;
+}
+
+.Preview {
+	color: var(--foreground-color-a);
+	font-size: 2.5rem;
+}
+
+.Input {
+	display: flex;
+	gap: var(--button-gap);
+	flex-direction: column;
+	height: calc(100% - var(--output-height));
+	padding: 0.5rem;
+}
+
+.Input-row {
+	flex: 1;
+	display: flex;
+	gap: var(--button-gap);
+}
+
+.Button {
+	flex: 1;
+	border-radius: 0.25rem;
+	font-size: 1.5rem;
+}
+
+.Input-row:first-of-type .Button {
+	--normal-color: var(--background-color-b);
+	--hover-color: var(--background-color-ba);
+}
+
+.Input-row .Button:last-of-type {
+	--text-color: var(--background-color-a);
+	--normal-color: var(--blue-a);
+	--hover-color: var(--blue-b);
+}
+
+.Button-large {
+	min-width: calc(50% - var(--button-gap) / 2);
+}
\ No newline at end of file
diff --git a/src/config/apps.config.js b/src/config/apps.config.js
index 172cc69..e0e5062 100644
--- a/src/config/apps.config.js
+++ b/src/config/apps.config.js
@@ -3,7 +3,9 @@ export const APPS = {
 	SETTINGS: "settings",
 	MEDIA_VIEWER: "media-viewer",
 	TEXT_EDITOR: "text-editor",
-	FILE_EXPLORER: "file-explorer"
+	FILE_EXPLORER: "file-explorer",
+	CALCULATOR: "calculator",
+	BROWSER: "browser",
 };
 
 export const APP_NAMES = {
@@ -11,7 +13,9 @@ export const APP_NAMES = {
 	SETTINGS: "Settings",
 	MEDIA_VIEWER: "Photos",
 	TEXT_EDITOR: "Notes",
-	FILE_EXPLORER: "Files"
+	FILE_EXPLORER: "Files",
+	CALCULATOR: "Maths",
+	BROWSER: "Browser",
 };
 
 export const APP_ICONS = {
@@ -20,4 +24,5 @@ export const APP_ICONS = {
 	MEDIA_VIEWER: `${process.env.PUBLIC_URL}/assets/apps/icons/${APPS.MEDIA_VIEWER}.svg`,
 	TEXT_EDITOR: `${process.env.PUBLIC_URL}/assets/apps/icons/${APPS.TEXT_EDITOR}.svg`,
 	FILE_EXPLORER: `${process.env.PUBLIC_URL}/assets/apps/icons/${APPS.FILE_EXPLORER}.svg`,
+	CALCULATOR: `${process.env.PUBLIC_URL}/assets/apps/icons/${APPS.CALCULATOR}.svg`,
 };
\ No newline at end of file
diff --git a/src/features/apps/appsManager.js b/src/features/apps/appsManager.js
index 737aea4..4dafcf4 100644
--- a/src/features/apps/appsManager.js
+++ b/src/features/apps/appsManager.js
@@ -5,22 +5,22 @@ import { WebView } from "../../components/apps/_utils/web-view/WebView.jsx";
 import { Terminal } from "../../components/apps/terminal/Terminal.jsx";
 import { TextEditor } from "../../components/apps/text-editor/TextEditor.jsx";
 import { Settings } from "../../components/apps/settings/Settings.jsx";
-// import { Calculator } from "../../components/apps/calculator/Calculator.jsx";
+import { Calculator } from "../../components/apps/calculator/Calculator.jsx";
 import Vector2 from "../math/vector2.js";
-import { APPS } from "../../config/apps.config.js";
+import { APPS, APP_NAMES } from "../../config/apps.config.js";
 import { Browser } from "../../components/apps/browser/Browser.jsx";
 import { IMAGE_FORMATS } from "../../config/apps/mediaViewer.config.js";
 
 export default class AppsManager {
 	static APPS = [
-		new App("Commands", APPS.TERMINAL, Terminal),
-		new App("Settings", APPS.SETTINGS, Settings),
-		new App("Photos", APPS.MEDIA_VIEWER, MediaViewer),
+		new App(APP_NAMES.TERMINAL, APPS.TERMINAL, Terminal),
+		new App(APP_NAMES.SETTINGS, APPS.SETTINGS, Settings),
+		new App(APP_NAMES.MEDIA_VIEWER, APPS.MEDIA_VIEWER, MediaViewer),
 		// new App("Browser", "browser"),
-		// new App("Calculator", "calculator", Calculator, { size: new Vector2(400, 600) }),
-		new App("Notes", APPS.TEXT_EDITOR, TextEditor),
+		new App(APP_NAMES.CALCULATOR, APPS.CALCULATOR, Calculator, { size: new Vector2(400, 600) }),
+		new App(APP_NAMES.TEXT_EDITOR, APPS.TEXT_EDITOR, TextEditor),
 		// new App("Code Editor", "code-editor"),
-		new App("Files", APPS.FILE_EXPLORER, FileExplorer),
+		new App(APP_NAMES.FILE_EXPLORER, APPS.FILE_EXPLORER, FileExplorer),
 		new App("Wordle", "wordle", WebView, {
 			source: "https://prozilla.dev/wordle",
 			size: new Vector2(400, 650)
@@ -33,7 +33,7 @@ export default class AppsManager {
 			source: "https://prozilla.dev/minesweeper",
 			size: new Vector2(500, 580)
 		}),
-		new App("Browser", "browser", Browser, {
+		new App(APP_NAMES.BROWSER, APPS.BROWSER, Browser, {
 			size: new Vector2(700, 500)
 		}),
 	];