Set minimum cell size

src/main.ts

@@ -12,7 +12,10 @@ const parsePattern = (pattern: string) => pattern.split('').map(x => Number.pars
 
 const xs = reactive(xs_).map((pattern) => parsePattern(pattern))
 const ys = reactive(ys_).map((pattern) => parsePattern(pattern))
-const cellSize = reactive(cellSize_).map(num => Number.parseInt(num, 10))
+const cellSize = reactive(cellSize_).map(num => {
+  const next = Number.parseInt(num, 10)
+  return Number.isNaN(next)|| next < 5 ? 5 : next
+})
 
 // available size for a2: 420 * 594
 const width = 420
@@ -91,8 +94,9 @@ $compile(
    ["h2", {}, "Settings"],
    ["div", {}, ["label", {}, "Grid size: ",
                 ["input", {
-                  type: "text",
-                  value: cellSize_,
+                  type: "number",
+                  min: "5",
+                  value: cellSize.deref()!,
                   oninput: $input(cellSize)
                 }]]],
    ["div", {}, ["label", {}, "X Pattern: ",