diff --git a/api/controller.js b/api/controller.js
index 949731c..5def039 100644
--- a/api/controller.js
+++ b/api/controller.js
@@ -1,7 +1,7 @@
 'use strict';
 
-exports.calculate = function(req, res) {
-  req.app.use(function(err, _req, res, next) {
+exports.calculate = function (req, res) {
+  req.app.use(function (err, _req, res, next) {
     if (res.headersSent) {
       return next(err);
     }
@@ -10,12 +10,14 @@ exports.calculate = function(req, res) {
     res.json({ error: err.message });
   });
 
-  // TODO: Add operator
   var operations = {
-    'add':      function(a, b) { return Number(a) + Number(b) },
-    'subtract': function(a, b) { return a - b },
-    'multiply': function(a, b) { return a * b },
-    'divide':   function(a, b) { return a / b },
+    'add': function (a, b) { return Number(a) + Number(b) },
+    'subtract': function (a, b) { return a - b },
+    'multiply': function (a, b) { return a * b },
+    'divide': function (a, b) { return a / b },
+    'power': function (a, b) { return Math.pow(a, b) },
+    'toBinary': function (a) { return parseInt(a).toString(2) },
+    'toDecimal': function (a) { return parseInt(a, 2).toString() }
   };
 
   if (!req.query.operation) {
@@ -28,17 +30,26 @@ exports.calculate = function(req, res) {
     throw new Error("Invalid operation: " + req.query.operation);
   }
 
+  // Validate operand1 for all operations
   if (!req.query.operand1 ||
-      !req.query.operand1.match(/^(-)?[0-9\.]+(e(-)?[0-9]+)?$/) ||
-      req.query.operand1.replace(/[-0-9e]/g, '').length > 1) {
+    !req.query.operand1.match(/^(-)?[0-9\.]+(e(-)?[0-9]+)?$/) ||
+    req.query.operand1.replace(/[-0-9e]/g, '').length > 1) {
     throw new Error("Invalid operand1: " + req.query.operand1);
   }
 
-  if (!req.query.operand2 ||
+  // Only validate operand2 for operations that need it
+  if (!['toBinary', 'toDecimal'].includes(req.query.operation)) {
+    if (!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);
+      throw new Error("Invalid operand2: " + req.query.operand2);
+    }
   }
 
-  res.json({ result: operation(req.query.operand1, req.query.operand2) });
+  // Call operation with appropriate number of arguments
+  const result = ['toBinary', 'toDecimal'].includes(req.query.operation)
+    ? operation(req.query.operand1)
+    : operation(req.query.operand1, req.query.operand2);
+
+  res.json({ result: result });
 };
diff --git a/public/client.js b/public/client.js
index 1c60f86..4aed2a1 100644
--- a/public/client.js
+++ b/public/client.js
@@ -17,21 +17,30 @@ var operand2 = 0;
 var operation = null;
 
 function calculate(operand1, operand2, operation) {
-    var uri = location.origin + "/arithmetic";
+    var uri = location.origin + "/arithmetic?operation=";
 
     // TODO: Add operator
     switch (operation) {
         case '+':
-            uri += "?operation=add";
+            uri += "add";
             break;
         case '-':
-            uri += "?operation=subtract";
+            uri += "subtract";
             break;
         case '*':
-            uri += "?operation=multiply";
+            uri += "multiply";
             break;
         case '/':
-            uri += "?operation=divide";
+            uri += "divide";
+            break;
+        case '^':
+            uri += "power";
+            break;
+        case 'bin':
+            uri += "toBinary";
+            break;
+        case 'dec':
+            uri += "toDecimal";
             break;
         default:
             setError();
@@ -39,7 +48,10 @@ function calculate(operand1, operand2, operation) {
     }
 
     uri += "&operand1=" + encodeURIComponent(operand1);
-    uri += "&operand2=" + encodeURIComponent(operand2);
+    // Only add operand2 for non-conversion operations
+    if (!['bin', 'dec'].includes(operation)) {
+        uri += "&operand2=" + encodeURIComponent(operand2);
+    }
 
     setLoading(true);
 
@@ -111,9 +123,16 @@ function signPressed() {
 }
 
 function operationPressed(op) {
-    operand1 = getValue();
-    operation = op;
-    state = states.operator;
+    if (op === 'bin' || op === 'dec') {
+        // For binary conversion, immediately calculate with current value
+        operand1 = getValue();
+        calculate(operand1, null, op);
+        state = states.complete;
+    } else {
+        operand1 = getValue();
+        operation = op;
+        state = states.operator;
+    }
 }
 
 function equalPressed() {
diff --git a/public/index.html b/public/index.html
index 400c454..1fec505 100644
--- a/public/index.html
+++ b/public/index.html
@@ -1,8 +1,11 @@
 <html>
   <head>
     <title>Calculator</title>
-    <link rel="stylesheet" href="default.css">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0">
+    <link rel="stylesheet" href="default.css" />
+    <meta
+      name="viewport"
+      content="width=device-width, initial-scale=1.0, maximum-scale=1.0"
+    />
     <script src="client.js"></script>
   </head>
   <body onLoad="setValue(0)">
@@ -11,7 +14,7 @@
         <div id="result"><span class="digit0">0</span></div>
       </div>
 
-      <div id="loading" style="visibility:hidden"></div>
+      <div id="loading" style="visibility: hidden"></div>
 
       <div class="box">
         <div class="calculator">
@@ -23,7 +26,9 @@
             <button class="btn" onClick="numberPressed(7)">7</button>
             <button class="btn" onClick="numberPressed(8)">8</button>
             <button class="btn" onClick="numberPressed(9)">9</button>
-            <button class="btn" onClick="operationPressed('/')">&divide;</button>
+            <button class="btn" onClick="operationPressed('/')">
+              &divide;
+            </button>
 
             <button class="btn" onClick="numberPressed(4)">4</button>
             <button class="btn" onClick="numberPressed(5)">5</button>
@@ -41,6 +46,12 @@
             <button class="btn" onClick="equalPressed()">=</button>
 
             <!-- TODO: Buttons -->
+            <!-- add a button for a power (or exponential) function -->
+            <button class="btn" onClick="operationPressed('^')">^</button>
+
+            <!-- Binary conversion buttons -->
+            <button class="btn" onClick="operationPressed('bin')">BIN</button>
+            <button class="btn" onClick="operationPressed('dec')">DEC</button>
           </div>
         </div>
       </div>
diff --git a/test/arithmetic.test.js b/test/arithmetic.test.js
index deded48..5db2284 100644
--- a/test/arithmetic.test.js
+++ b/test/arithmetic.test.js
@@ -93,15 +93,12 @@ describe('Arithmetic', function () {
         });
     });
 
-// TODO: Challenge #1
- 
-
-    describe('Multiplication', function () {
-        it('multiplies two positive integers', function (done) {
-            request.get('/arithmetic?operation=multiply&operand1=21&operand2=2')
+    describe('Subtraction', function () {
+        it('subtracts two positive integers', function (done) {
+            request.get('/arithmetic?operation=subtract&operand1=42&operand2=21')
                 .expect(200)
                 .end(function (err, res) {
-                    expect(res.body).to.eql({ result: 42 });
+                    expect(res.body).to.eql({ result: 21 });
                     done();
                 });
         });
@@ -147,6 +144,37 @@ describe('Arithmetic', function () {
         });
     });
 
+    describe('Power', function () {
+        it('raises a positive integer to a positive integer exponent', function (done) {
+            request.get('/arithmetic?operation=power&operand1=2&operand2=3')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 8 });
+                    done();
+                });
+        })
+    });
+
+    describe('Binary Conversion', function () {
+        it('converts decimal to binary', function (done) {
+            request.get('/arithmetic?operation=toBinary&operand1=42')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: "101010" });
+                    done();
+                });
+        });
+
+        it('converts binary to decimal', function (done) {
+            request.get('/arithmetic?operation=toDecimal&operand1=101010')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: "42" });
+                    done();
+                });
+        });
+    });
+
     describe('Division', function () {
         it('divides a positive integer by an integer factor ', function (done) {
             request.get('/arithmetic?operation=divide&operand1=42&operand2=2')