change BNF (but not implementation of BNF) for parsing, to handle layers, and also change minimum key in layer tree to be 1

fcore/parser/brace-dfa.sml

@@ -5,8 +5,13 @@ struct
   val final = 2
 
   fun makeStart i =
-    let val chr = Char.chr i
-    in if chr = #"{" orelse chr = #"}" then final else dead
+    let
+      val chr = Char.chr i
+    in
+      if chr = #"{" orelse chr = #"}" orelse chr = #"[" orelse chr = #"]" then
+        final
+      else
+        dead
     end
 
   val deadTable = SpaceDfa.deadTable

fcore/parser/lexer.sml

@@ -26,6 +26,8 @@ struct
           else if min = lastBrace then
             if str = "{" then SOME (lastBrace, T.L_BRACE :: acc)
             else if str = "}" then SOME (lastBrace, T.R_BRACE :: acc)
+            else if str = "[" then SOME (lastBrace, T.L_BRACKET :: acc)
+            else if str = "]" then SOME (lastBrace, T.R_BRACKET :: acc)
             else NONE
           else
             NONE

fcore/parser/parser.md

@@ -4,14 +4,16 @@ The parsing functionality is for saving and loading from a custom file format.
 
 The BNF for the custom file format is below.
 
-Terminals are surrounded by `**` to the left and right. (rule)+ means "1 o more".
+Terminals are surrounded by `**` to the left and right. (rule)+ means "1 or more".
 
 ```
 int ::= (0-9)+
 
 item ::= **{** int int int int int int int int **}**
 
-grid ::= int int **{** (item)+ **}**
+grid ::= **[** item **]**
+
+grid_list ::= int int **{** (grid)+ **}**
 ```
 
 The first two `int`s in the grid `int int **{** (item)+ **}**` always follow the order: `canvasWidth canvasHeight`.

fcore/parser/tokens.sml

@@ -1,7 +1,2 @@
 structure Tokens =
-struct
-  datatype t =
-    L_BRACE
-  | R_BRACE
-  | INT of int
-end
+struct datatype t = L_BRACE | R_BRACE | L_BRACKET | R_BRACKET | INT of int end