This year we went to ChaosStack with my friends. It was fine, nothing special, we sucked, but we had fun.

However, last year I applied with a different team. We had a hard time deciding the technologies to do the selection task with, as we couldn't find a language that all three of us would know. We finally agreed on C++, which wasn't exactly the best tool for the job (calling rest apis) but at least we all knew it a little. We divided the work, agreed on texting one another if we can't solve something, and I thought we were done.
Fast forward 3 days before the deadline, I text them when we could meet to connect the things.
No response.
Next morning I learned that they left to a maths camp (that's been held on those exact days for the past 10 years) and wouldn't come back until after the competition.