diff --git a/.eslintrc.js b/.eslintrc.js
index 9e80f9a..8015305 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -3,7 +3,7 @@ module.exports = {
         "browser": true,
         "es2021": true,
         "mocha": true,
-        "request": true
+        "node": true
     },
     "extends": "eslint:recommended",
     "overrides": [
diff --git a/api/controller.js b/api/controller.js
index 949731c..6dea8e0 100644
--- a/api/controller.js
+++ b/api/controller.js
@@ -16,6 +16,9 @@ exports.calculate = function(req, res) {
     'subtract': function(a, b) { return a - b },
     'multiply': function(a, b) { return a * b },
     'divide':   function(a, b) { return a / b },
+    'modulo':   function(a, b) { return a % b },
+    'sqrt':     function(a) { return Math.sqrt(a) },
+    'power2':   function(a) { return Math.pow(a, 2) },
   };
 
   if (!req.query.operation) {
@@ -29,14 +32,18 @@ exports.calculate = function(req, res) {
   }
 
   if (!req.query.operand1 ||
-      !req.query.operand1.match(/^(-)?[0-9\.]+(e(-)?[0-9]+)?$/) ||
+      !req.query.operand1.match(/^(-)?[0-9.]+(e(-)?[0-9]+)?$/) ||
       req.query.operand1.replace(/[-0-9e]/g, '').length > 1) {
     throw new Error("Invalid operand1: " + req.query.operand1);
   }
 
-  if (!req.query.operand2 ||
-      !req.query.operand2.match(/^(-)?[0-9\.]+(e(-)?[0-9]+)?$/) ||
-      req.query.operand2.replace(/[-0-9e]/g, '').length > 1) {
+  // Some operations only require one operand
+  var unaryOperations = ['sqrt', 'power2'];
+  var requiresOperand2 = !unaryOperations.includes(req.query.operation);
+
+  if (requiresOperand2 && (!req.query.operand2 ||
+      !req.query.operand2.match(/^(-)?[0-9.]+(e(-)?[0-9]+)?$/) ||
+      req.query.operand2.replace(/[-0-9e]/g, '').length > 1)) {
     throw new Error("Invalid operand2: " + req.query.operand2);
   }
 
diff --git a/public/client.js b/public/client.js
index 1c60f86..e78ff43 100644
--- a/public/client.js
+++ b/public/client.js
@@ -33,6 +33,15 @@ function calculate(operand1, operand2, operation) {
         case '/':
             uri += "?operation=divide";
             break;
+        case '%':
+            uri += "?operation=modulo";
+            break;
+        case '√':
+            uri += "?operation=sqrt";
+            break;
+        case '^2':
+            uri += "?operation=power2";
+            break;
         default:
             setError();
             return;
@@ -111,9 +120,18 @@ function signPressed() {
 }
 
 function operationPressed(op) {
-    operand1 = getValue();
-    operation = op;
-    state = states.operator;
+    // Check if it's a unary operation
+    if (op === '√' || op === '^2') {
+        // For unary operations, calculate immediately
+        var currentValue = getValue();
+        calculate(currentValue, 0, op); // Pass 0 as dummy operand2
+        state = states.complete;
+    } else {
+        // Binary operation - store operand1 and wait for operand2
+        operand1 = getValue();
+        operation = op;
+        state = states.operator;
+    }
 }
 
 function equalPressed() {
@@ -138,7 +156,7 @@ document.addEventListener('keypress', (event) => {
         numberPressed(event.key);
     } else if (event.key == '.') {
         decimalPressed();
-    } else if (event.key.match(/^[-*+/]$/)) {
+    } else if (event.key.match(/^[-*+/%]$/)) {
         operationPressed(event.key);
     } else if (event.key == '=') {
         equalPressed();
diff --git a/public/index.html b/public/index.html
index 400c454..ec9bdd9 100644
--- a/public/index.html
+++ b/public/index.html
@@ -16,9 +16,10 @@
       <div class="box">
         <div class="calculator">
           <div class="calculator-buttons">
-            <button class="btn span-2"></button>
             <button class="btn" onClick="clearPressed()">C</button>
             <button class="btn" onClick="clearPressed()">CE</button>
+            <button class="btn" onClick="operationPressed('%')">%</button>
+            <button class="btn" onClick="operationPressed('√')">√</button>
 
             <button class="btn" onClick="numberPressed(7)">7</button>
             <button class="btn" onClick="numberPressed(8)">8</button>
@@ -37,10 +38,10 @@
 
             <button class="btn" onClick="numberPressed(0)">0</button>
             <button class="btn" onClick="decimalPressed()">.</button>
+            <button class="btn" onClick="operationPressed('^2')">x²</button>
             <button class="btn" onClick="operationPressed('+')">+</button>
-            <button class="btn" onClick="equalPressed()">=</button>
 
-            <!-- TODO: Buttons -->
+            <button class="btn span-2" onClick="equalPressed()">=</button>
           </div>
         </div>
       </div>
diff --git a/test/arithmetic.test.js b/test/arithmetic.test.js
index deded48..1c44521 100644
--- a/test/arithmetic.test.js
+++ b/test/arithmetic.test.js
@@ -95,6 +95,110 @@ describe('Arithmetic', function () {
 
 // TODO: Challenge #1
  
+    describe('Modulo', function () {
+        it('calculates modulo of two positive integers', function (done) {
+            request.get('/arithmetic?operation=modulo&operand1=10&operand2=3')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 1 });
+                    done();
+                });
+        });
+        it('calculates modulo with zero remainder', function (done) {
+            request.get('/arithmetic?operation=modulo&operand1=10&operand2=5')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 0 });
+                    done();
+                });
+        });
+        it('calculates modulo of negative and positive integer', function (done) {
+            request.get('/arithmetic?operation=modulo&operand1=-10&operand2=3')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: -1 });
+                    done();
+                });
+        });
+        it('calculates modulo with floating point numbers', function (done) {
+            request.get('/arithmetic?operation=modulo&operand1=5.5&operand2=2')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 1.5 });
+                    done();
+                });
+        });
+    });
+
+    describe('Square Root', function () {
+        it('calculates square root of positive integer', function (done) {
+            request.get('/arithmetic?operation=sqrt&operand1=9')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 3 });
+                    done();
+                });
+        });
+        it('calculates square root of zero', function (done) {
+            request.get('/arithmetic?operation=sqrt&operand1=0')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 0 });
+                    done();
+                });
+        });
+        it('calculates square root of floating point number', function (done) {
+            request.get('/arithmetic?operation=sqrt&operand1=2.25')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 1.5 });
+                    done();
+                });
+        });
+        it('calculates square root of large number', function (done) {
+            request.get('/arithmetic?operation=sqrt&operand1=100')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 10 });
+                    done();
+                });
+        });
+    });
+
+    describe('Power of Two', function () {
+        it('calculates power of two for positive integer', function (done) {
+            request.get('/arithmetic?operation=power2&operand1=5')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 25 });
+                    done();
+                });
+        });
+        it('calculates power of two for zero', function (done) {
+            request.get('/arithmetic?operation=power2&operand1=0')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 0 });
+                    done();
+                });
+        });
+        it('calculates power of two for negative integer', function (done) {
+            request.get('/arithmetic?operation=power2&operand1=-3')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 9 });
+                    done();
+                });
+        });
+        it('calculates power of two for floating point number', function (done) {
+            request.get('/arithmetic?operation=power2&operand1=2.5')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 6.25 });
+                    done();
+                });
+        });
+    });
 
     describe('Multiplication', function () {
         it('multiplies two positive integers', function (done) {