diff --git a/es_test.lua b/es_test.lua
new file mode 100644
index 0000000..bf76479
--- /dev/null
+++ b/es_test.lua
@@ -0,0 +1,110 @@
+local floor = math.floor
+local ipairs = ipairs
+local log = math.log
+local print = print
+
+local ars = require("ars")
+local snes = require("snes")
+local xnes = require("xnes")
+
+-- try it all out on a dummy problem.
+
+local function square(x) return x * x end
+
+-- this function's global minimum is arange(dims) + 1.
+-- xNES should be able to find it almost exactly.
+local function spherical(x)
+    local sum = 0
+    for i, v in ipairs(x) do sum = sum + square(v - i) end
+    -- we need to negate this to turn it into a maximization problem.
+    return -sum
+end
+
+-- i'm just copying settings from hardmaru's simple_es_example.ipynb.
+local iterations = 3000 --4000
+local dims = 100
+local popsize = dims + 1
+local sigma_init = 0.5
+--local es = xnes.Xnes(dims, popsize, 0.1, sigma_init)
+--local es = snes.Snes(dims, popsize, 0.1, sigma_init)
+--local es = ars.Ars(dims, floor(popsize / 2), floor(popsize / 2), 1.0, sigma_init, true)
+local es = ars.Ars(dims, popsize, popsize, 1.0, sigma_init, true)
+es.min_refresh = 0.7 -- FIXME: needs a better interface.
+
+if false then -- TODO: delete me
+    local nn = require("nn")
+    local util = require("util")
+    local insert = table.insert
+    local scored = nn.arange(10)
+    local indices = ars.collect_best_indices(scored, 3, true)
+    for i, ind in ipairs(indices) do
+        print(ind, ":", scored[ind * 2 - 1], scored[ind * 2 - 0])
+    end
+    local top_rewards = {}
+    for _, ind in ipairs(indices) do
+        insert(top_rewards, scored[ind * 2 - 1])
+        insert(top_rewards, scored[ind * 2 - 0])
+    end
+    -- this shouldn't make a difference to the final print:
+    top_rewards = util.normalize_sums(top_rewards)
+    print(nn.pp(top_rewards))
+    local _, reward_dev = util.calc_mean_dev(top_rewards)
+    print(reward_dev)
+    for i, ind in ipairs(indices) do
+        local pos = top_rewards[i * 2 - 1]
+        local neg = top_rewards[i * 2 - 0]
+        local reward = pos - neg
+        reward = reward / reward_dev
+        print(reward)
+    end
+    do return end
+end
+
+local asked = nil -- for caching purposes.
+local noise = nil -- for caching purposes.
+local current_cost = spherical(es:params())
+
+for i=1, iterations do
+    if getmetatable(es).__index == snes.Snes then
+        asked, noise = es:ask_mix()
+    elseif getmetatable(es).__index == ars.Ars then
+        asked, noise = es:ask()
+    else
+        asked, noise = es:ask(asked, noise)
+    end
+    local scores = {}
+    for i, v in ipairs(asked) do
+        scores[i] = spherical(v)
+    end
+
+    if getmetatable(es).__index == ars.Ars then
+        es:tell(scores)--, current_cost) -- use lips
+    else
+        es:tell(scores)
+    end
+
+    current_cost = spherical(es:params())
+    --if i % 100 == 0 then
+    if i % 100 == 0 then
+        local sigma = es.sigma
+        if getmetatable(es).__index == snes.Snes then
+            sigma = 0
+            for i, v in ipairs(es.std) do sigma = sigma + v end
+            sigma = sigma / #es.std
+        end
+        local inconvergence = sigma / sigma_init
+        local fmt = "fitness at iteration %i: %.4f (%.4f)"
+        print(fmt:format(i, current_cost, log(inconvergence) / log(10)))
+    end
+end
+
+-- note: this metric doesn't include the "fitness at iteration" evaluations,
+--       because those aren't actually used to step towards the optimum.
+print(("optimized in %i function evaluations"):format(es.evals))
+
+local s = ''
+for i, v in ipairs(es:params()) do
+    s = s..("%.8f"):format(v)
+    if i ~= es.dim then s = s..', ' end
+end
+print(s)
diff --git a/extra.lua b/extra.lua
new file mode 100644
index 0000000..c0aa538
--- /dev/null
+++ b/extra.lua
@@ -0,0 +1,62 @@
+local function strpad(num, count, pad)
+    num = tostring(num)
+    return (pad:rep(count)..num):sub(#num)
+end
+
+local function add_zeros(num, count)
+    return strpad(num, count - 1, '0')
+end
+
+local function mixed_sorter(a, b)
+    a = type(a) == 'number' and add_zeros(a, 16) or tostring(a)
+    b = type(b) == 'number' and add_zeros(b, 16) or tostring(b)
+    return a < b
+end
+
+-- loosely based on http://lua-users.org/wiki/SortedIteration
+-- the original didn't make use of closures for who knows why
+local function order_keys(t)
+    local oi = {}
+    for key in pairs(t) do
+        table.insert(oi, key)
+    end
+    table.sort(oi, mixed_sorter)
+    return oi
+end
+
+local function opairs(t, cache)
+    local oi = cache and cache[t] or order_keys(t)
+    if cache then
+        cache[t] = oi
+    end
+    local i = 0
+    return function()
+        i = i + 1
+        local key = oi[i]
+        if key then return key, t[key] end
+    end
+end
+
+local function traverse(path)
+    if not path then return end
+    local parent = _G
+    local key
+    for w in path:gfind("[%w_]+") do
+        if key then
+            parent = rawget(parent, key)
+            if type(parent) ~= 'table' then return end
+        end
+        key = w
+    end
+    if not key then return end
+    return {parent=parent, key=key}
+end
+
+return {
+    strpad = strpad,
+    add_zeros = add_zeros,
+    mixed_sorter = mixed_sorter,
+    order_keys = order_keys,
+    opairs = opairs,
+    traverse = traverse,
+}
diff --git a/monitor_tiles.lua b/monitor_tiles.lua
new file mode 100644
index 0000000..111d3b5
--- /dev/null
+++ b/monitor_tiles.lua
@@ -0,0 +1,54 @@
+-- keep track of which blocks are actually seen in the game.
+-- play back an all-levels TAS with this script running.
+
+local floor = math.floor
+local open = io.open
+local pairs = pairs
+local print = print
+
+local util = require("util")
+local R = memory.readbyteunsigned
+local W = memory.writebyte
+local function S(addr) return util.signbyte(R(addr)) end
+
+local game = require("smb")  -- just for advance()
+
+local serial = require "serialize"
+local serialize = serial.serialize
+local deserialize = serial.deserialize
+
+local fn = 'seen_tiles.lua'
+local seen = deserialize(fn) or {}
+
+local function mark_tile(sx, sy, kind)
+    if not seen[kind] then
+        seen[kind] = true
+        print(("%02X"):format(kind))
+        serialize(fn, seen)
+    end
+end
+
+local function handle_tiles()
+    --local tile_col = R(0x6A0)
+    local tile_scroll = floor(R(0x73F) / 16) + R(0x71A) * 16
+    local tile_scroll_remainder = R(0x73F) % 16
+    for y = 0, 12 do
+        for x = 0, 16 do
+            local col = (x + tile_scroll) % 32
+            local t
+            if col < 16 then
+                t = R(0x500 + y * 16 + (col % 16))
+            else
+                t = R(0x5D0 + y * 16 + (col % 16))
+            end
+            local sx = x * 16 + 8 - tile_scroll_remainder
+            local sy = y * 16 + 40
+            mark_tile(sx, sy, t)
+        end
+    end
+end
+
+while true do
+    handle_tiles()
+    game.advance()
+end
diff --git a/presets.lua b/presets.lua
index 47736f1..37d9965 100644
--- a/presets.lua
+++ b/presets.lua
@@ -72,6 +72,28 @@ make_preset{
     sigma_decay = 0.008,
 }
 
+make_preset{
+    name = 'snes2',
+    parent = 'big-scroll-reduced',
+
+    es = 'snes',
+    deterministic = true,
+    deviation = 0.01,
+    negate_trials = false,
+    epoch_trials = 60,
+    min_refresh = 2/3,
+    param_rate = 0.368,
+    param_decay = 0.0138,
+    sigma_rate = 0.100,
+    sigma_decay = 0.0051,
+}
+
+make_preset{
+    name = 'snes3',
+    parent = 'snes2',
+    min_refresh = 1/3,
+}
+
 make_preset{
     name = 'xnes',
     parent = 'big-scroll-reduced',
diff --git a/rescale.lua b/rescale.lua
new file mode 100644
index 0000000..b3976d2
--- /dev/null
+++ b/rescale.lua
@@ -0,0 +1,15 @@
+local f = assert(io.open("params-ars4.txt", "r"))
+local data = f:read("*a")
+f:close()
+local values = {}
+for v in data:gmatch("[^\r\n]+") do
+    table.insert(values, tonumber(v))
+end
+
+for i, v in ipairs(values) do
+    values[i] = v * 100
+end
+
+for i, v in ipairs(values) do
+    print(v)
+end
diff --git a/running.lua b/running.lua
new file mode 100644
index 0000000..969f1ab
--- /dev/null
+++ b/running.lua
@@ -0,0 +1,183 @@
+local huge = math.huge
+local ipairs = ipairs
+local open = io.open
+local sqrt = math.sqrt
+
+local nn = require("nn")
+local Base = require("Base")
+
+-- https://github.com/modestyachts/ARS/blob/master/code/filter.py
+-- http://www.johndcook.com/blog/standard_deviation/
+local Stats = Base:extend()
+local Normalizer = Base:extend()
+
+function Stats:init(shape)
+    self._n = 0
+    self._M = nn.zeros(shape)
+    self._S = nn.zeros(shape)
+end
+
+function Stats:push(x)
+    assert(nn.prod(x.shape) == nn.prod(self._M.shape), "sizes mismatch")
+    local n1 = self._n
+    self._n = self._n + 1
+    if self._n == 1 then
+        nn.copy(x, self._M)
+    else
+        local delta = {}
+        for i, v in ipairs(self._M) do delta[i] = x[i] - v end
+        for i, v in ipairs(self._M) do self._M[i] = v + delta[i] / self._n end
+        for i, v in ipairs(self._S) do self._S[i] = v + delta[i] * delta[i] * n1 / self._n end
+    end
+end
+
+function Stats:var()
+    local out = {}
+    if self._n == 1 then
+        for i, v in ipairs(self._M) do out[i] = v * v end
+    else
+        for i, v in ipairs(self._S) do out[i] = v / (self._n - 1) end
+    end
+    return out
+end
+
+function Stats:dev()
+    local out = self:var()
+    for i, v in ipairs(out) do out[i] = sqrt(v) end
+    return out
+end
+
+function Normalizer:init(shape, demean, destd)
+    if demean == nil then demean = true end
+    if destd == nil then destd = true end
+    self.shape = shape
+    self.demean = demean
+    self.destd = destd
+    self.rs = Stats(shape)
+    self.mean = nn.zeros(shape)
+    self.std = nn.zeros(shape)
+    for i = 1, #self.std do self.std[i] = 1 end
+end
+
+function Normalizer:process(x)
+    local out = nn.copy(x)
+    if self.demean then
+        for i, v in ipairs(out) do out[i] = out[i] - self.mean[i] end
+    end
+    if self.destd then
+        for i, v in ipairs(out) do out[i] = out[i] / (self.std[i] + 1e-8) end
+    end
+    return out
+end
+
+function Normalizer:update()
+    nn.copy(self.rs._M, self.mean) -- FIXME: HACK
+    nn.copy(self.rs:dev(), self.std)
+    -- Set values for std less than 1e-7 to +inf
+    -- to avoid dividing by zero. State elements
+    -- with zero variance are set to zero as a result. 
+    for i, v in ipairs(self.std) do
+        if v < 1e-7 then self.std[i] = huge end
+    end
+end
+
+function Normalizer:push(x, update)
+    self.rs:push(x)
+    if update == nil or update then self:update() end
+    return self:process(x)
+end
+
+function Normalizer:default_filename()
+    return ('stats%07i.txt'):format(nn.prod(self.shape))
+end
+
+function Normalizer:save(fn)
+    local fn = fn or self:default_filename()
+    local f = open(fn, 'w')
+    if f == nil then error("Failed to save stats to file "..fn) end
+    f:write(self.rs._n)
+    f:write('\n')
+    for i, v in ipairs(self.rs._M) do
+        f:write(v)
+        f:write('\n')
+    end
+    for i, v in ipairs(self.rs._S) do
+        f:write(v)
+        f:write('\n')
+    end
+    f:close()
+end
+
+function Normalizer:load(fn)
+    local fn = fn or self:default_filename()
+    local f = open(fn, 'r')
+    if f == nil then error("Failed to load stats from file "..fn) end
+
+    local i = 0
+    local split_M = 1
+    local split_S = split_M + nn.prod(self.shape)
+    for line in f:lines() do
+        i = i + 1
+        local n = tonumber(line)
+        if n == nil then
+            error("Failed reading line "..tostring(i).." of file "..fn)
+        end
+
+        if i <= split_M then
+            self.rs._n = n
+        elseif i <= split_S then
+            self.rs._M[i - split_M] = n
+        else
+            self.rs._S[i - split_S] = n
+        end
+    end
+    f:close()
+
+    self:update()
+end
+
+--[[
+
+-- basic tests
+
+local dims = 20
+local rs = Stats(dims)
+local x = nn.zeros(dims)
+
+for i = 1, #x do x[i] = nn.normal() end
+rs:push(x)
+print(nn.pp(rs:dev()))
+
+for j = 1, 10000 do
+    for i = 1, #x do x[i] = nn.normal() end
+    rs:push(x)
+end
+print(nn.pp(rs:dev()))
+
+--
+
+local ms = Normalizer(dims)
+local exp = math.exp
+local y
+
+for i = 1, #x do x[i] = exp(nn.normal()) end
+y = ms:push(x)
+print(nn.pp(y))
+
+for j = 1, 10000 do
+    for i = 1, #x do x[i] = exp(nn.normal()) end
+    y = ms:push(x)
+end
+print(nn.pp(y))
+
+print("mean:")
+print(nn.pp(ms.mean))
+print("stdev:")
+print(nn.pp(ms.std))
+
+--]]
+
+return {
+    Stats = Stats,
+    Normalizer = Normalizer,
+}
diff --git a/seen_tiles.lua b/seen_tiles.lua
new file mode 100644
index 0000000..90ad5b7
--- /dev/null
+++ b/seen_tiles.lua
@@ -0,0 +1,59 @@
+return {
+	[0] = true,
+	[16] = true,
+	[17] = true,
+	[18] = true,
+	[19] = true,
+	[20] = true,
+	[21] = true,
+	[22] = true,
+	[23] = true,
+	[24] = true,
+	[25] = true,
+	[26] = true,
+	[27] = true,
+	[28] = true,
+	[29] = true,
+	[30] = true,
+	[31] = true,
+	[32] = true,
+	[33] = true,
+	[34] = true,
+	[35] = true,
+	[36] = true,
+	[37] = true,
+	[38] = true,
+	[81] = true,
+	[82] = true,
+	[84] = true,
+	[85] = true,
+	[86] = true,
+	[87] = true,
+	[88] = true,
+	[89] = true,
+	[90] = true,
+	[91] = true,
+	[92] = true,
+	[93] = true,
+	[94] = true,
+	[95] = true,
+	[96] = true,
+	[97] = true,
+	[98] = true,
+	[99] = true,
+	[100] = true,
+	[101] = true,
+	[102] = true,
+	[103] = true,
+	[104] = true,
+	[105] = true,
+	[107] = true,
+	[108] = true,
+	[137] = true,
+	[192] = true,
+	[193] = true,
+	[194] = true,
+	[195] = true,
+	[196] = true,
+	[197] = true,
+}
diff --git a/serialize.lua b/serialize.lua
new file mode 100644
index 0000000..44f1726
--- /dev/null
+++ b/serialize.lua
@@ -0,0 +1,76 @@
+-- it's simple, dumb, unsafe, incomplete, and it gets the damn job done
+
+local type = type
+local extra = require "extra"
+local opairs = extra.opairs
+local tostring = tostring
+local open = io.open
+local strfmt = string.format
+local strrep = string.rep
+
+local function kill_bom(s)
+    if #s >= 3 and s:byte(1)==0xEF and s:byte(2)==0xBB and s:byte(3)==0xBF then
+        return s:sub(4)
+    end
+    return s
+end
+
+local function sanitize(v)
+    local force = type(v) == 'string' and v:sub(1, 1):match('%d')
+    force = force and true or false
+    return type(v) == 'string' and strfmt('%q', v) or tostring(v), force
+end
+
+local function _serialize(value, writer, level)
+    level = level or 1
+    if type(value) == 'table' then
+        local indent = strrep('\t', level)
+        writer('{\n')
+        for key,value in opairs(value) do
+            local sane, force = sanitize(key)
+            local keyval = (sane == '"'..key..'"' and not force) and key or '['..sane..']'
+            writer(indent..keyval..' = ')
+            _serialize(value, writer, level + 1)
+            writer(',\n')
+        end
+        writer(strrep('\t', level - 1)..'}')
+    else
+        local sane, force = sanitize(value)
+        writer(sane)
+    end
+end
+
+local function _deserialize(script)
+    local f = loadstring(kill_bom(script))
+    if f ~= nil then
+        return f()
+    else
+        print('WARNING: no function to deserialize with')
+        return nil
+    end
+end
+
+local function serialize(path, value)
+    local file = open(path, 'w')
+    if not file then return end
+    file:write("return ")
+    _serialize(value, function(...)
+        file:write(...)
+    end)
+    file:write("\n")
+    file:close()
+end
+
+local function deserialize(path)
+    local file = open(path, 'r')
+    if not file then return end
+    local script = file:read('*a')
+    local value = _deserialize(script)
+    file:close()
+    return value
+end
+
+return {
+    serialize = serialize,
+    deserialize = deserialize,
+}
diff --git a/snes.lua b/snes.lua
index f2532d5..38fd3bb 100644
--- a/snes.lua
+++ b/snes.lua
@@ -3,7 +3,6 @@
 -- http://www.jmlr.org/papers/volume15/wierstra14a/wierstra14a.pdf
 -- not to be confused with the Super Nintendo Entertainment System.
 
-local abs = math.abs
 local assert = assert
 local exp = math.exp
 local floor = math.floor
diff --git a/util.lua b/util.lua
index 1b98428..b8b5b89 100644
--- a/util.lua
+++ b/util.lua
@@ -115,7 +115,7 @@ local function unperturbed_rank(rewards, unperturbed_reward)
     local nth_place = 1
     for i, v in ipairs(rewards) do
         if v > unperturbed_reward then
-            nth_place = nth_place +  1
+            nth_place = nth_place + 1
         end
     end
     return nth_place