Even more detailed information will be available in the Magic Comprehensive Rules
Mythical Beast Medusa X LIGHT Level 4 [ Spellcaster / PendulumEffect ] ATK 1500 DEF 1500 P Scale 4 If you have no card in your other Pendulum Zone: You can target 1 monster in your GY that you can place a Spell Counter on
Each one teaches a core Magic concept, rewards a clear and forgiving strategy, and wont ask you to memorize a rulebook before your first turn
Because of the way Kroxa and Kunoros' ability resolves, you can sacrifice it in response to the reanimation clause, sacrificing it to the Altar, to mill six cards and then exile five of them to return Kroxa and Kunoros to play, triggering its ability again in an infinite loop
2) Look at how symbols are defined in src/data/expansion_symbols.json for examples
These two things alone are quite useful little tricks