Learn in this order
If you are new to sobosuba, begin with the how-to guide and play one short run using mostly gentle shots. The goal is to understand the opposite-direction pull, equal-value rule and danger line before worrying about score.
Next, use the strategy guide to make each shot serve a specific job: merge, store, open or recover. Planning with the NEXT preview and maintaining one usable route into the lower pile will improve consistency more than shooting harder.
Finish with the physics guide when you want to understand why a target moved, why a shot rebounded or why a lower merge reorganized the whole stack. The shape is part of the simulation, so those details directly explain better play.
Play while you read
The guides are reference material, but sobosuba is easiest to learn by alternating reading with short runs. Open the browser game, test one idea and return when the pile gives you a new question. No account or download is required.