diff --git a/experiments/tree-sitter-test/grammar.js b/experiments/tree-sitter-test/grammar.js
index 5fb773f..2de25d1 100644
--- a/experiments/tree-sitter-test/grammar.js
+++ b/experiments/tree-sitter-test/grammar.js
@@ -12,14 +12,14 @@ module.exports = grammar({
             "fn",
             $.identifier,
             $.parameter_list,
-            $._type,
+            optional($._type),
             $.block,
         ),
         parameter_list: $ => seq("(", /* TODO */ ")"),
 
         block: $ => seq(
             "{",
-            repeat($._statement),
+            repeat(optional($._statement)),
             "}"
         ),
 
@@ -29,7 +29,10 @@ module.exports = grammar({
 
         _return_statement: $ => seq("return", $._expression, ";"),
 
-        _expression: $ => choice($.identifier),
+        _expression: $ => choice($.identifier, $.unary, $.binary),
+
+        unary: $ => prec(4, choice(seq("-", $._expression), seq("!", $._expression))),
+        binary: $ => choice(prec.left(2, seq($._expression, "*", $._expression)), prec.left(1, seq($._expression, "+", $._expression))),
 
         _type: $ => "bool",
 
diff --git a/experiments/tree-sitter-test/test/corpus/test.txt b/experiments/tree-sitter-test/test/corpus/test.txt
index 3c0a61c..ab26e36 100644
--- a/experiments/tree-sitter-test/test/corpus/test.txt
+++ b/experiments/tree-sitter-test/test/corpus/test.txt
@@ -1,8 +1,9 @@
 =============
 Initial test
 =============
+fn main() {
 
-hello
+}
 
 ----
 
@@ -13,7 +14,7 @@ hello
 Another
 ====
 
-fn main() { }
+fn main() bool { }
 
 ------
 ()