fix redrawing map tile

game/init.fnl

@@ -148,8 +148,29 @@
   [:tya] [:and 0xe0]
   [:sta vm.TOP :x])
 
-(vm:word :drawtile-at ; xy --
+(vm:def :itile-at ; yx -- itile
-  :drop) ; todo
+  [:lda (- maph 1)]
+  [:sec]
+  [:sbc vm.TOPH :x]
+  [:asl :a] ; x2
+  [:asl :a] ; x4
+  [:sta vm.TOPH :x]
+  [:asl :a] ; x8
+  [:asl :a] ; x16
+  [:clc] [:adc vm.TOPH :x] ; x20
+  [:adc vm.TOP :x]
+  [:sta vm.TOP :x]
+  [:lda #(hi ($1:lookup-addr :map))]
+  [:sta vm.TOPH :x]
+  [:lda [vm.TOP :x]]
+  [:sta vm.TOP :x]
+  [:lda 0]
+  [:sta vm.TOPH :x])
+
+(vm:word :drawtile-at ; yx --
+  :dup :yx>screen :swap
+  :itile-at :lookup-tile
+  :drawtile)
 
 (vm:def :last-key ; -- key
   (vm:reserve)