diff --git a/samples/hp48/index.html b/samples/hp48/index.html
index d8eef66..6a5d1f4 100644
--- a/samples/hp48/index.html
+++ b/samples/hp48/index.html
@@ -286,15 +286,21 @@
       });
     }
 
-    function render() {
-    const stack = calc.stack;
-    const names = ['T', 'Z', 'Y', 'X'];
-    const lines = [];
-    for (let i = 3; i >= 0; i -= 1) {
-      const value = stack[i];
-      lines.push(`<div class="stack-line"><div class="label">${names[3 - i]}</div><div>${value !== undefined ? calc.formatNumber(value) : ''}</div></div>`);
+    function getLineValue(line) {
+      if (line === 0 && calc.isEditing) {
+        return calc.inputValue;
+      }
+      return calc.stack[line];
     }
 
+    function render() {
+      const names = ['T', 'Z', 'Y', 'X'];
+      const lines = [];
+      for (let line = 3; line >= 0; line -= 1) {
+        const value = getLineValue(line);
+        lines.push(`<div class="stack-line"><div class="label">${names[3 - line]}</div><div>${value !== undefined && value !== '' ? calc.formatNumber(value) : ''}</div></div>`);
+      }
+
       stackEl.innerHTML = lines.join('');
       displayEl.textContent = calc.isEditing ? `ENTERING: ${calc.inputValue}` : 'READY';
       inputValueLabel.textContent = calc.inputValue || '∅';
@@ -304,22 +310,40 @@
       errorEl.textContent = '';
     }
 
+    function pushEditingValueIfNeeded() {
+      if (!calc.isEditing) return;
+      if (calc.inputValue !== '') {
+        const value = calc.parseInputValue(calc.inputValue);
+        if (calc.stack.length >= calc.maxSize) {
+          throw new Error('Stack overflow');
+        }
+        calc.stack.unshift(value);
+        if (calc.stack.length > 4) calc.stack.length = 4;
+      }
+      calc.inputValue = '';
+      calc.isEditing = false;
+      syncInputFromState();
+    }
+
     function execute(name) {
       try {
         if (name === 'swap') {
-          if (calc.isEditing) calc.command('enter');
+          pushEditingValueIfNeeded();
           if (calc.stack.length >= 2) calc.swap(0, 1);
         } else if (name === 'drop') {
+          pushEditingValueIfNeeded();
           if (calc.stack.length >= 1) calc.remove(0);
         } else if (name === 'clear') {
           calc.clear();
         } else if (name === 'enter') {
-          if (calc.isEditing) calc.command('enter');
-        } else if (name === 'pi' || name === 'e') {
-          calc.command(name);
+          if (calc.isEditing) {
+            pushEditingValueIfNeeded();
+          }
         } else {
+          pushEditingValueIfNeeded();
           calc.command(name);
         }
+        syncInputFromState();
         render();
       } catch (error) {
         errorEl.textContent = error.message;
@@ -338,13 +362,29 @@
       input.value = calc.inputValue;
     }
 
+    function editXWithKey(key) {
+      if (!calc.isEditing) {
+        pushEditingValueIfNeeded();
+        calc.isEditing = true;
+        calc.inputValue = '';
+      }
+      if (key === 'Backspace') {
+        calc.inputValue = calc.inputValue.slice(0, -1);
+      } else {
+        calc.inputValue += key;
+      }
+      if (calc.inputValue === '') {
+        calc.isEditing = false;
+      }
+      syncInputFromState();
+    }
+
     screen.addEventListener('keydown', (event) => {
       try {
         if (event.key === 'Enter') {
           event.preventDefault();
           if (calc.isEditing) {
             calc.command('enter');
-            syncInputFromState();
           }
           render();
           return;
@@ -353,9 +393,7 @@
         if (event.key === 'Backspace') {
           event.preventDefault();
           if (calc.isEditing) {
-            calc.inputValue = calc.inputValue.slice(0, -1);
-            if (calc.inputValue === '') calc.isEditing = false;
-            syncInputFromState();
+            editXWithKey('Backspace');
             render();
           }
           return;
@@ -363,8 +401,7 @@
 
         if (isInputChar(event.key)) {
           event.preventDefault();
-          calc.input(event.key);
-          syncInputFromState();
+          editXWithKey(event.key);
           render();
           return;
         }
@@ -380,8 +417,7 @@
 
         if (keyMap[event.key]) {
           event.preventDefault();
-          calc.command(keyMap[event.key]);
-          render();
+          execute(keyMap[event.key]);
         }
       } catch (error) {
         errorEl.textContent = error.message;