added visualization for day 3 puzzle 1

src/day3/puzzle1.typ

@@ -1,7 +1,8 @@
 #import "/src/utils.typ": *
 
+#let reg = regex("mul\((\d{1,3}),(\d{1,3})\)")
 #let solve(input) = {
-  let matches = input.matches(regex("mul\((\d{1,3}),(\d{1,3})\)"))
+  let matches = input.matches(reg)
   let total = matches.map(m => {
     m.captures.map(int)
               .product()
@@ -9,8 +10,24 @@
   return total
 }
 
+#let visualize(input) = {
+  [
+    #set text(size: 1.2em)
+    #show reg: it => {
+      let m = it.text.match(reg)
+      let v = m.captures.map(int).product()
+      math.underbrace(
+        highlight(fill: red, raw(it.text)),
+        text(size: 1.5em, str(v))
+      )
+    }
+    #raw(input)
+  ]
+}
+
 #show-puzzle(
   3, 1,
   solve,
-  example: ("1": 161)
+  example: ("1": 161),
+  visualize: visualize
 )