Updated Part 1(JS)

finished/Piggybank.sol

@@ -0,0 +1,28 @@
+pragma solidity ^0.4.0;
+
+contract PiggyBank {
+    uint256 private balance;
+    address public owner;
+
+    function PiggyBank() public {
+        owner = msg.sender;
+        balance = 0;
+    }
+
+    function deposit() public payable returns (uint256) {
+        balance += msg.value;
+        return balance;
+    }
+
+    function withdraw(uint256 withdrawAmount)
+        public
+        returns (uint256 remainingBal)
+    {
+        require(msg.sender == owner);
+        balance -= withdrawAmount;
+
+        msg.sender.transfer(withdrawAmount);
+
+        return balance;
+    }
+}

finished/src/index.css

@@ -41,3 +41,30 @@ header {
 #encryptMessageInput {
   margin-bottom: 1rem;
 }
+
+.error-div {
+  margin-bottom: 12px;
+}
+
+.error-message {
+  min-height: 32px;
+  border: 1px solid #e88f97;
+  color: #24292e;
+  background: #fcf2f3;
+  border-radius: 8px;
+  display: flex;
+  justify-content: flex-start;
+  align-items: center;
+  padding: 8px 10px;
+}
+.error-message-icon {
+  margin-right: 8px;
+  flex: 0 0 auto;
+}
+.error-message-text {
+  overflow: auto;
+}
+
+.warning-invisible {
+  display: none;
+}