diff --git a/transpiler.js b/transpiler.js
index 12f17b2..d4b8db7 100644
--- a/transpiler.js
+++ b/transpiler.js
@@ -1,17 +1,50 @@
 /**
  * Transpiles a string of Hi source code into JavaScript.
+ * This is a foundational, regex-based implementation.
+ * It will be replaced by a proper AST-based generator in the future.
  * @param {string} sourceCode The Hi source code.
  * @returns {string} The equivalent JavaScript code.
  */
 export function hi2js(sourceCode) {
-  // This will be replaced by a proper AST-based generator.
   return sourceCode
-    // Comments: // ...
-    .replace(/^\s*\/\/.*/gm, (match) => match)
-    // Declaration: name: value -> let name = value;
-    .replace(/^(?!.*\/\/.*)([\w$]+)\s*:\s*(.*)/gm, 'let $1 = $2;')
-    // Assignment: name = value -> name = value;
-    .replace(/^(?!.*\/\/.*)([\w$]+)\s*=\s*([^:;].*)/gm, '$1 = $2;')
-    // Global output: _(...) -> console.log(...);
-    .replace(/^(?!.*\/\/.*)\s*_\((.*)\)/gm, 'console.log($1);');
+    // Preserve comments
+    .replace(/^\s*\/\/.*/gm, match => match)
+
+    // Function Declaration: name: (params) { body }
+    .replace(/^([\w$]+)\s*:\s*\(([^)]*)\)\s*\{([\s\S]*?)\s*\}/gm, (match, name, params, body) => {
+        const expressions = body.trim().split('\n').map(l => l.trim()).filter(Boolean);
+        const lastExpression = expressions.pop() || 'undefined';
+        const functionBody = [...expressions, `return ${lastExpression}`].join(';\n  ');
+        return `let ${name} = (${params}) => {\n  ${functionBody};\n};`;
+    })
+
+    // Block (Object) Declaration: name: { members }
+    .replace(/^([\w$]+)\s*:\s*\{([\s\S]*?)\s*\}/gm, (match, name, members) => {
+        const jsMembers = members
+            .trim()
+            .split('\n')
+            .map(line => line.trim().replace(/^([\w$]+)\s*:\s*(.*)$/, '$1: $2'))
+            .join(',\n  ');
+        return `let ${name} = {\n  ${jsMembers}\n};`;
+    })
+
+    // Simple Declaration: name: value
+    .replace(/^([\w$]+)\s*:\s*(.*)/gm, 'let $1 = $2;')
+
+    // Assignment: name = value
+    .replace(/^([\w$]+)\s*=\s*([^:;].*)/gm, '$1 = $2;')
+
+    // Global output: _(...)
+    .replace(/^\s*_\((.*)\)/gm, 'console.log($1);')
+    
+    // Semicolon insertion for remaining expressions
+    .split('\n')
+    .map(line => {
+        const trimmed = line.trim();
+        if (trimmed.length > 0 && !trimmed.endsWith(';') && !trimmed.endsWith('{') && !trimmed.endsWith('}') && !trimmed.startsWith('//')) {
+            return line + ';';
+        }
+        return line;
+    })
+    .join('\n');
 }