# Spaced repetition prompt lenses

In his guide on writing prompts, Andy Matuschak lists five lenses for writing prompts:

• Attributes and tendencies
• Similarities and differences
• Parts and wholes
• Causes and effects
• Significance and implications

Here I want to brainstorm some more lenses, in line with my reflections on five years of conceptual Anki where I said I wanted to be more methodical about my memory practice. Having a list of lenses helps me to go through each one to see if cards can be made using that lens.

Here’s what I’ve come up with so far:

• counterfactual: what goes wrong if you do this other thing? what happens if you change this thing? – i guess this is still causes and effects, although not all counterfactuals are causal.
• numbers and parameters… can something ever have the parameter set to X? e.g. can a certain form of diophantine equation ever have just one solution? Can a system of linear equations ever have just two solutions? This one can overlap with causes and effects, significance and implications (why must the parameter be set to X?), attributes and tendencies (sometimes, always, never), depending on what the prompt is. but this seems like a useful additional lens.
• limitations … if we were restricted in a certain way, could we still accomplish something?
• generalizations and restrictions: does this thing generalize? Andy might say this is just parts and wholes.
• expression in terms of something else: e.g. express lcm in terms of gcd.
• draw it: what does a derivative look like?
• metaphors/analogies: immune book has a lot of this, e.g. macrophage as raging rhino.
• computations and algorithm execution: e.g. compute gcd(5,0).