diff --git a/static/js/components/commandForm.js b/static/js/components/commandForm.js
index 5b6b70e..3519db4 100644
--- a/static/js/components/commandForm.js
+++ b/static/js/components/commandForm.js
@@ -73,7 +73,19 @@ window.openBuildingModal = function() {
     const clickable = !isMaxed && !isLocked;
     const onclick   = clickable ? `onclick="window.selectBuilding('${key}','${nameGr}')"` : '';
 
-    return `<div class="bld-card ${cardClass}${isSelected ? ' bld-selected' : ''}" ${onclick}>
+    // Build tooltip for locked buildings
+    let tooltip = '';
+    if (isLocked && missingKeys.length > 0) {
+      const missingDeps = data.missing_dependencies;
+      const lines = missingKeys.map(k => {
+        const dep = missingDeps[k];
+        const depNameGr = window.BUILDING_NAMES_GR[k] || k;
+        return `${depNameGr} (Επίπεδο ${dep.needed_level || dep.needed || '?'})`;
+      });
+      tooltip = `title="Απαιτείται:\n${lines.join('\n')}"`;
+    }
+
+    return `<div class="bld-card ${cardClass}${isSelected ? ' bld-selected' : ''}" ${onclick} ${tooltip}>
       <span class="bld-level">${level}</span>
       <span class="bld-icon">${icon}</span>
       <span class="bld-name">${nameGr}</span>