diff --git a/Sources/PMCalc/Operand.swift b/Sources/PMCalc/Operand.swift
new file mode 100644
index 0000000..83f94e3
--- /dev/null
+++ b/Sources/PMCalc/Operand.swift
@@ -0,0 +1,8 @@
+enum Operand {
+    case add
+    case sub
+    case mul
+    case div
+    case pow
+    case sqrt
+}
\ No newline at end of file
diff --git a/Sources/PMCalc/PMCalc.swift b/Sources/PMCalc/PMCalc.swift
index ca0afc8..1b5fd93 100644
--- a/Sources/PMCalc/PMCalc.swift
+++ b/Sources/PMCalc/PMCalc.swift
@@ -7,85 +7,125 @@ import CMath
 @main
 struct PMCalc: App {
     let app = AdwaitaApp(id: "me.thealgorithm476.PMCalc.PMCalc")
+    @State
+    var vm = ViewModel()
 
     var scene: Scene {
         Window(id: "main") { window in
             VStack(spacing: 8) {
-                Text("Calculations here...")
+                Text(vm.display)
                     .selectable(false)
+                    .title2()
+                    .halign(.end)
                 VStack(spacing: 8) {
                     HStack(spacing: 8) {
-                        Button("AC") {}
+                        Button("AC") {
+                            vm.clear()
+                        }
                             .keyboardShortcut("c", app: app)
                             .hexpand()
                             .destructive()
-                        Button("") {}
+                        Button("^") {
+                            vm.operation(.pow)
+                        }
                             .hexpand()
-                            .flat()
                         Button("%") {}
                             .keyboardShortcut("percent", app: app)
                             .hexpand()
-                        Button("/") {}
+                        Button("/") {
+                            vm.operation(.div)
+                        }
                             .keyboardShortcut("slash", app: app)
                             .hexpand()
                     }
                     .vexpand()
                     HStack(spacing: 8) {
-                        Button("7") {}
+                        Button("7") {
+                            vm.addNumber(7)
+                        }
                             .keyboardShortcut("7", app: app)
                             .hexpand()
-                        Button("8") {}
+                        Button("8") {
+                            vm.addNumber(8)
+                        }
                             .keyboardShortcut("8", app: app)
                             .hexpand()
-                        Button("9") {}
+                        Button("9") {
+                            vm.addNumber(9)
+                        }
                             .keyboardShortcut("9", app: app)
                             .hexpand()
-                        Button("*") {}
+                        Button("*") {
+                            vm.operation(.mul)
+                        }
                             .keyboardShortcut("asterisk", app: app)
                             .hexpand()
                     }
                     .vexpand()
                     HStack(spacing: 8) {
-                        Button("4") {}
+                        Button("4") {
+                            vm.addNumber(4)
+                        }
                             .keyboardShortcut("4", app: app)
                             .hexpand()
-                        Button("5") {}
+                        Button("5") {
+                            vm.addNumber(5)
+                        }
                             .keyboardShortcut("5", app: app)
                             .hexpand()
-                        Button("6") {}
+                        Button("6") {
+                            vm.addNumber(6)
+                        }
                             .keyboardShortcut("6", app: app)
                             .hexpand()
-                        Button("-") {}
+                        Button("-") {
+                            vm.operation(.sub)
+                        }
                             .keyboardShortcut("minus", app: app)
                             .hexpand()
                     }
                     .vexpand()
                     HStack(spacing: 8) {
-                        Button("1") {}
+                        Button("1") {
+                            vm.addNumber(1)
+                        }
                             .keyboardShortcut("1", app: app)
                             .hexpand()
-                        Button("2") {}
+                        Button("2") {
+                            vm.addNumber(2)
+                        }
                             .keyboardShortcut("2", app: app)
                             .hexpand()
-                        Button("3") {}
+                        Button("3") {
+                            vm.addNumber(3)
+                        }
                             .keyboardShortcut("3", app: app)
                             .hexpand()
-                        Button("+") {}
+                        Button("+") {
+                            vm.operation(.add)
+                        }
                             .keyboardShortcut("plus", app: app)
                             .hexpand()
                     }
                     .vexpand()
                     HStack(spacing: 8) {
-                        Button("0") {}
+                        Button("0") {
+                            vm.addNumber(0)
+                        }
                             .keyboardShortcut("0", app: app)
                             .hexpand()
-                        Button("") {}
+                        Button("sq") {
+                            vm.operation(.sqrt)
+                        }
                             .hexpand()
-                            .flat()
-                        Button(",") {}
+                        Button(",") {
+                            vm.addComma()
+                        }
                             .keyboardShortcut("comma", app: app)
                             .hexpand()
-                        Button("=") {}
+                        Button("=") {
+                            vm.calculate()
+                        }
                             .keyboardShortcut("equal", app: app)
                             .hexpand()
                     }
diff --git a/Sources/PMCalc/ViewModel.swift b/Sources/PMCalc/ViewModel.swift
new file mode 100644
index 0000000..9dc96ba
--- /dev/null
+++ b/Sources/PMCalc/ViewModel.swift
@@ -0,0 +1,73 @@
+import Adwaita
+import CMath
+
+struct ViewModel {
+    private var numberBuffer: String = ""
+    private var number1: Double? = nil
+    private var number2: Double? = nil
+    private var operand: Operand? = nil
+    @State
+    private(set) var display: String = ""
+
+    mutating func clear() {
+        numberBuffer = ""
+        number1 = nil
+        number2 = nil
+        operand = nil
+        display = ""
+    }
+
+    mutating func addComma() {
+        guard !numberBuffer.isEmpty else { return }
+
+        numberBuffer.append(",")
+        display = numberBuffer
+    }
+
+    mutating func addNumber(_ number: UInt8) {
+        if numberBuffer.isEmpty { display = "" } // Reset display after new number is added to cleared buffer
+
+        numberBuffer.append(String(number))
+        display = numberBuffer
+    }
+
+    mutating func operation(_ operand: Operand) {
+        guard !numberBuffer.isEmpty && number1 == nil else { return }
+
+        self.operand = operand
+        if number1 == nil { number1 = Double(numberBuffer) }
+        else { number2 = Double(numberBuffer) }
+        numberBuffer = ""
+
+        if operand == .sqrt {
+            display = String(sqrt(number1!))
+            number1 = nil
+            self.operand = nil
+        }
+    }
+
+    mutating func calculate() {
+        number2 = Double(numberBuffer)
+        numberBuffer = ""
+
+        var result: Double = 0.0
+
+        switch operand {
+        case .add:
+            result = add_nums(number1!, number2!)
+        case .sub:
+            result = sub_nums(number1!, number2!)
+        case .mul:
+            result = mul_nums(number1!, number2!)
+        case .div:
+            result = div_nums(number1!, number2!)
+        case .pow:
+            result = pow(number1!, number2!)
+        case .sqrt, .none:
+            // do nothing
+            print("Attempting to apply Square Root to nothing!")
+        }
+
+        display = String(result)
+    }
+}
\ No newline at end of file