Kepler & K2 provide long-baseline, high-precision photometry for exoplanet and astrophysics research.
The basic and most common additional rule for Doubles play is that where a Double exists at the end of any train, the Double must then be 'satisfied' (laid against) in the next turn, even if the Double is on another player's train that is not marked.
All it takes is about 10-20 minutes, and never more than 30 minutes. If you want to do conditioning as a finisher pick some type of high intensity movement like a sled push, bike sprint, jump rope sprint or kettlebell swing. Do 4-6 rounds of 30 seconds, hard and fast. Rest 60-120 seconds between rounds.