diff --git a/src/main/java/tdd/setup/Calculator.java b/src/main/java/tdd/setup/Calculator.java
index 171f6d6..4d6ff48 100644
--- a/src/main/java/tdd/setup/Calculator.java
+++ b/src/main/java/tdd/setup/Calculator.java
@@ -3,7 +3,7 @@
 // behaviour inspired by https://www.online-calculator.com/
 public class Calculator {
 
-    private String screen = "0";
+    private String screen = "";
 
     private double latestValue;
 
@@ -15,7 +15,7 @@ public String readScreen() {
     public void pressDigitKey(int digit) {
         if(digit > 9 || digit < 0) throw new IllegalArgumentException();
 
-        if(latestOperation.isEmpty()) {
+        if(latestOperation.isEmpty() || latestValue != 0.0) {
             screen = screen + digit;
         } else {
             latestValue = Double.parseDouble(screen);
@@ -52,4 +52,5 @@ public void pressEquals() {
         screen = Double.toString(result);
         if(screen.endsWith(".0")) screen = screen.substring(0,screen.length()-2);
     }
+
 }
diff --git a/src/test/java/tdd/setup/CalculatorTest.java b/src/test/java/tdd/setup/CalculatorTest.java
index 3bf16e9..4a56608 100644
--- a/src/test/java/tdd/setup/CalculatorTest.java
+++ b/src/test/java/tdd/setup/CalculatorTest.java
@@ -16,4 +16,38 @@ void calculatorCanDoTwoPlusTwo() {
         calc.pressEquals();
         assertEquals("4", calc.readScreen());
     }
+    @Test
+    @DisplayName("should display result after subtracting two positive numbers")
+    void calculatorCanDoTwoMinusTwo() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(2);
+        calc.pressOperationKey("-");
+        calc.pressDigitKey(2);
+        calc.pressEquals();
+        assertEquals("0", calc.readScreen());
+    }
+    @Test
+    @DisplayName("should display result after changing a Number to negative")
+    void calculatorCanDoNegative() {
+        Calculator calc = new Calculator();
+        calc.pressNegative();
+        calc.pressDigitKey(2);
+        assertEquals("-2", calc.readScreen());
+    }
+
+    @Test
+    @DisplayName("should display result after multiplying two positive two digit numbers")
+    void calculatorCanMultiplyTwoTwoDigitNumbers() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(2);
+        calc.pressDigitKey(0);
+        calc.pressOperationKey("x");
+        calc.pressDigitKey(2);
+        calc.pressDigitKey(5);
+        calc.pressEquals();
+        assertEquals("500", calc.readScreen());
+    }
+
+
+
 }