diff --git a/core/src/doc.rs b/core/src/doc.rs
index 6f91415..5bd3fbb 100644
--- a/core/src/doc.rs
+++ b/core/src/doc.rs
@@ -81,10 +81,35 @@ fn is_ident(s: &str) -> bool {
 }
 
 pub fn classify_document(text: &str) -> Vec<ClassifiedLine> {
-    text.lines()
-        .enumerate()
-        .map(|(i, line)| classify_line(i, line))
-        .collect()
+    let mut result = Vec::new();
+    let mut in_block_comment = false;
+
+    for (i, line) in text.lines().enumerate() {
+        if in_block_comment {
+            let cl = ClassifiedLine { index: i, kind: LineKind::Comment, content: line.to_string() };
+            if line.contains("*/") {
+                in_block_comment = false;
+            }
+            result.push(cl);
+            continue;
+        }
+
+        let trimmed = line.trim();
+
+        if trimmed.starts_with("/*") {
+            if trimmed.contains("*/") && trimmed.find("*/").unwrap() > trimmed.find("/*").unwrap() {
+                // single-line block comment
+            } else {
+                in_block_comment = true;
+            }
+            result.push(ClassifiedLine { index: i, kind: LineKind::Comment, content: line.to_string() });
+            continue;
+        }
+
+        result.push(classify_line(i, line));
+    }
+
+    result
 }
 
 #[cfg(test)]
@@ -132,4 +157,28 @@ mod tests {
         let c = classify_line(0, "Some notes about the project");
         assert_eq!(c.kind, LineKind::Markdown);
     }
+
+    #[test]
+    fn single_line_block_comment() {
+        let lines = classify_document("/* hello */");
+        assert_eq!(lines.len(), 1);
+        assert_eq!(lines[0].kind, LineKind::Comment);
+    }
+
+    #[test]
+    fn multiline_block_comment() {
+        let lines = classify_document("/* start\nmiddle\nend */\nlet x = 5");
+        assert_eq!(lines.len(), 4);
+        assert_eq!(lines[0].kind, LineKind::Comment);
+        assert_eq!(lines[1].kind, LineKind::Comment);
+        assert_eq!(lines[2].kind, LineKind::Comment);
+        assert_eq!(lines[3].kind, LineKind::Cordial);
+    }
+
+    #[test]
+    fn block_comment_then_code() {
+        let lines = classify_document("/* comment */\n/= 2 + 3");
+        assert_eq!(lines[0].kind, LineKind::Comment);
+        assert_eq!(lines[1].kind, LineKind::Eval);
+    }
 }