Tracker: Course/Arrange

[NiloCK]

Allow for "comparative" course browsing with user-supplied difficulty comparisons between presented cards.

Basics

• add multi-card viewer / selector
• make accessible from course info page
• appropriately scale the k-factor on elo adjustments
• investigate tagged-elo adjustments
• investigate provisional-elo adjustments (for slotting in new content)
• enable 'sequential' playing of audio-enabled cards
  • w/ a visual indicator for which card is currently playing

UI

• improve transition to next comparison
• improve "grouping" of vote button with its card

Iterations

• refactor as best-of-n rather than hard coded 2 cards

Particulars

• restrict random elo value in the elo-compare workflow to the elo bounds of the course
• consider (reject): default random behaviour to sub-user elo.
  • Not exactly relevant given the below step
• consider (do this): default card surfacing to "least experienced" cards (via 139 prioritize new content #185)
• consider (leaning toward do): default card surfacing should mix low-experience cards with high-experience cards with similar ELO ratings
• consider: new cards should initialize with the course ceiling ELO.
  • /study session difficulty mismatches will then be experienced in the "too easy" mode rather than "too hard"
  • mismatch burden shifted from low-investment beginners to higher-investment experienced users