Update root challenges and placeholders for May 20th Meetup

challenges.md

@@ -9,13 +9,13 @@ Welcome to our monthly 3D printing challenges! Each month features a unique them
 
 ## Active Challenge
 
-### March 2026: "Bring an Experiment"
+### April 2026: "Bring an Experiment (Round 2!)"
 
-**Theme**: Try something new, crazy, or wild! Bring in an experiment.
+**Theme**: Try something new, crazy, or wild! Bring in an experiment, even if it's a failed print / spaghetti.
 
 **Key Details**:
 
-- **Model**: Any experimental print
+- **Model**: Any experimental print (failures encouraged!)
 - **Goal**: Share what you tried, why you tried it, and if it worked or failed.
 - **Voting**: Group vote for favorite experimental attempt
 
@@ -23,17 +23,17 @@ Welcome to our monthly 3D printing challenges! Each month features a unique them
 
 ## Upcoming Challenge
 
-### April 2026: "[Theme TBD]"
+### May 2026: "[Theme TBD]"
 
 **Status**: Planning in progress
 
 **Expected Timeline**:
 
-- **Announcement**: April meeting (April 2026)
-- **Submission Period**: May 2026
-- **Judging**: May 2026
+- **Announcement**: May meeting (May 20th, 2026)
+- **Submission Period**: June 2026
+- **Judging**: June 2026
 
-**[View Challenge Placeholder](./challenges/April-2026/readme.md)**
+**[View Challenge Placeholder](./challenges/May-2026/readme.md)**
 
 ## Challenge Archive