diff --git a/.gitignore b/.gitignore
index 0cea664..0dd8231 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 */*/input
+*/*/output
 .*.swp
diff --git a/12023/13/13.lua b/12023/13/13.lua
new file mode 100644
index 0000000..ef5fb18
--- /dev/null
+++ b/12023/13/13.lua
@@ -0,0 +1,120 @@
+io.input("input")
+
+rows = {}
+cols = {}
+len = 0
+ngroup = 1
+sum1 = 0
+
+function reset()
+    r = 0
+    vindexes = {}
+    hindexes = {}
+    rows = {}
+end
+
+function two_consecutives(t)
+    if #t==1 then return nil
+    elseif #t==2 then
+        if t[1]+1==t[2] then return {table.pack(t[1], t[2])} end
+    else
+        local consecutives = {}
+        for i=1,#t-1 do
+            if t[i]+1==t[i+1] then 
+                table.insert(consecutives, table.pack(t[i], t[i+1]))
+            end
+        end
+        if #consecutives>0 then return consecutives end
+    end
+    return nil
+end
+
+function reflection(indexes, nums, N)
+    print(N)
+    local consecutives = {}
+    for num, ix in pairs(indexes) do
+        print(num, table.concat(ix,","))
+        if #ix==4 then print("HERE") end
+        local cs = two_consecutives(ix)
+        if cs then
+            for _, c in ipairs(cs) do
+                table.insert(consecutives, c)
+            end
+        end
+    end
+    print("consecutives")
+    if #consecutives>0 then
+        for _, c in ipairs(consecutives) do
+            local a,b = table.unpack(c)
+            local x,y = a,b
+            print(a,b)
+            local reflected = true
+            while reflected and x>=1 and y<=N do
+                print("testing",x,y,nums[x],nums[y])
+                if nums[x]~=nums[y] then 
+                    reflected = false
+                end
+                x,y = x-1, y+1
+            end
+            print(reflected)
+            if reflected then return a end
+        end
+    else
+        return nil
+    end
+end
+
+function end_of_group()
+    for j=1,len do
+        local vnum = cols[j]
+        if not vindexes[vnum] then vindexes[vnum]={} end
+        table.insert(vindexes[vnum], j)
+        --print(cols[j])
+    end
+
+    print("vindexes")
+    local vr = reflection(vindexes, cols, len)
+
+    print("hindexes")
+    local hr = reflection(hindexes, rows, r)
+
+    if vr then
+        sum1 = sum1 + vr
+    end
+    if hr then
+        sum1 = sum1 + 100*hr
+    end
+
+    ngroup = ngroup + 1
+    -- reset
+    reset()
+    print()
+end
+
+reset()
+for line in io.lines() do
+    if line:find("[%#%.]") then
+        if r==0 then
+            len = #line
+            for i=1,len do cols[i]=0 end
+            print("G",ngroup)
+        end
+        r = r+1
+        local hnum = 0
+        for i=1,len do
+            local char = line:sub(i,i)
+            local bit = char=="#" and 1 or 0
+            hnum = (hnum << 1) | bit
+            cols[i] = (cols[i]<<1) | bit
+        end
+        table.insert(rows, hnum)
+        if not hindexes[hnum] then hindexes[hnum]={} end
+        table.insert(hindexes[hnum],r)
+        --print(r,line,hnum)
+    else
+        end_of_group()
+    end
+end
+end_of_group()
+
+print("part 1", sum1)
diff --git a/12023/13/test b/12023/13/test
new file mode 100644
index 0000000..3b6b5cc
--- /dev/null
+++ b/12023/13/test
@@ -0,0 +1,15 @@
+#.##..##.
+..#.##.#.
+##......#
+##......#
+..#.##.#.
+..##..##.
+#.#.##.#.
+
+#...##..#
+#....#..#
+..##..###
+#####.##.
+#####.##.
+..##..###
+#....#..#
diff --git a/12023/13/test1 b/12023/13/test1
new file mode 100644
index 0000000..4337eef
--- /dev/null
+++ b/12023/13/test1
@@ -0,0 +1,13 @@
+##.###..#.###.###
+.###.##......#.##
+..#..##..##.##.##
+..#..##..##.##.##
+.###.##......#.##
+##.###..#.###.###
+..#.#.#..#..###..
+.#.#.#.#.#.#####.
+.#.#.#.#.#.#####.
+..#.#.#..#..###..
+######..#.###.###
+.###.##......#.##
+..#..##..##.##.##
\ No newline at end of file