update format definition

Author: eudoxia0

README.md

@@ -40,18 +40,73 @@ $ hashcards drill $DIRNAME
 
 ## Format
 
-A deck is a Markdown file. Blank lines separate flashcards. Question-answer cards use the slash character to separate the sides:
+This section describes the text format used by hashcards.
+
+### Basic Cards
+
+Question-answer flashcards are written like this:
 
 ```
-What is the order of a group? / The cardinality of its underlying set.
+Q: What is the order of a group?
+A: The cardinality of its underlying set.
 ```
 
-Cloze cards use square brackets to denote cloze deletions:
+Both the question and the answer can span multiple lines:
+
+```
+Q: List the PGM minerals.
+A:
+
+- ruthenium
+- rhodium
+- palladium
+- osmium
+- iridium
+- platinum
+```
+
+### Cloze Cards
+
+Cloze cards start with the `C:` tag, and use square brackets to denote cloze deletions:
 
 ```
-The [order] of a group is [the cardinality of its underlying set].
+C: The [order] of a group is [the cardinality of its underlying set].
 ```
 
+Again, cloze cards can span multiple lines:
+
+```
+C:
+Better is the sight of the eyes than the wandering of the
+desire: this is also vanity and vexation of spirit.
+
+— [Ecclesiastes] [6]:[9]
+```
+
+### Term-Definition Cards
+
+This is a special shorthand. This:
+
+```
+T: lithification
+D: The process of turning loose sediment into rock.
+```
+
+Is equivalent to writing this:
+
+```
+Q: Define: lithification
+A: The process of turning loose sediment into rock.
+
+Q: Term for:
+
+The process of turning loose sediment into rock.
+
+A: lithification
+```
+
+The constraint here is that the term must be a single line of text.
+
 ## Prior Art
 
 - [org-fc](https://github.com/l3kn/org-fc)