Randomize questions on every Anki regen

Also make explanation section slightly more readable

amateurfunk_anki.py

@@ -33,6 +33,7 @@ import json
 import os
 import random
 import re
+import secrets
 import shutil
 import sqlite3
 import sys
@@ -1415,7 +1416,7 @@ CARD_CSS = """
   font-size: 15px;
   line-height: 1.5;
   color: #333;
-  font-style: italic;
+  font-style: normal;
 }
 .af-explanation-header {
   font-family: Arial, sans-serif;
@@ -1451,6 +1452,28 @@ CARD_CSS = """
   color: #1a73e8;
   text-decoration: none;
 }
+.nightMode .af-explanation,
+.card.nightMode .af-explanation {
+  border-top-color: #555;
+  color: #ddd;
+}
+.nightMode .af-explanation-header,
+.card.nightMode .af-explanation-header {
+  color: #aaa;
+}
+.nightMode .af-explanation-source,
+.card.nightMode .af-explanation-source {
+  color: #bbb;
+}
+.nightMode .af-explanation-source a,
+.card.nightMode .af-explanation-source a {
+  color: #8ab4f8;
+}
+.nightMode .af-explanation-low-confidence,
+.card.nightMode .af-explanation-low-confidence {
+  background: #4a3510;
+  color: #ffd77a;
+}
 """
 
 
@@ -1481,6 +1504,13 @@ def build_epoch_from_manifest(manifest, override_epoch=None):
         ) from e
 
 
+def resolve_shuffle_seed(seed):
+    """Return the explicit shuffle seed or a fresh one for this build."""
+    if seed is not None:
+        return seed
+    return secrets.token_hex(16)
+
+
 def build_all(data_dir, out_dir, seed, override_epoch=None, explanations_path=None):
     """Build every category's `.apkg` and return their result dicts.
 
@@ -1546,8 +1576,11 @@ def _parse_args(argv):
     )
     parser.add_argument(
         "--seed",
-        default="amateurfunk-anki-v1",
-        help="deterministic seed for answer shuffling",
+        default=None,
+        help=(
+            "deterministic seed for answer shuffling; omit to reshuffle "
+            "answers on every build"
+        ),
     )
     parser.add_argument(
         "--epoch",
@@ -1573,11 +1606,12 @@ def _parse_args(argv):
 def main(argv=None):
     """Top-level entry point. Returns an exit code; never raises."""
     args = _parse_args(argv)
+    seed = resolve_shuffle_seed(args.seed)
     try:
         results = build_all(
             args.data,
             args.out,
-            seed=args.seed,
+            seed=seed,
             override_epoch=args.epoch,
             explanations_path=args.explanations,
         )