diff --git a/spddiff.avs b/spddiff.avs
new file mode 100644
index 0000000..17ba663
--- /dev/null
+++ b/spddiff.avs
@@ -0,0 +1,171 @@
+global fontsize = 26
+
+function DiffClip(clip c, int diff)
+{ BlankClip(c, diff).Subtitle(String(-diff), align=5, size=c.Height / 8) }
+
+function PadWithDiff(clip c, int len)
+{ c.FrameCount < len ? c + DiffClip(c, len - c.FrameCount) : c }
+
+function DualMonoToStereo(clip left, clip right)
+{ MergeChannels(ConvertToMono(left), ConvertToMono(right)) }
+
+function MergeHoriz(clip left, clip right, int audio_index)
+{
+	v = Overlay(AddBorders(left, 0, 0, right.Width, 0), right, left.Width, 0)
+	return audio_index == 0 \
+	? AudioDub(v, DualMonoToStereo(left, right)) \
+	: audio_index == 1 ? AudioDub(v, left) \
+	: audio_index == 2 ? AudioDub(v, right) \
+	: v
+}
+
+function MergeVert(clip top, clip bottom, int audio_index)
+{
+	v = Overlay(AddBorders(top, 0, 0, 0, bottom.Height), bottom, 0, top.Height)
+	return audio_index == 0 \
+	? AudioDub(v, DualMonoToStereo(top, bottom)) \
+	: audio_index == 1 ? AudioDub(v, top) \
+	: audio_index == 2 ? AudioDub(v, bottom) \
+	: v
+}
+
+function Cmp(clip left, clip right)
+{
+	frames = max(left.FrameCount, right.FrameCount)
+	left = PadWithDiff(left, frames)
+	right = PadWithDiff(right, frames)
+	return MergeHoriz(left, right, 0)
+}
+
+function TextHoriz(clip c, int frames, string left, string right)
+{
+	size = fontsize
+	tleft  = BlankClip(c, frames, height=size).Subtitle(left,  align=2, size=size)
+	tright = BlankClip(c, frames, height=size).Subtitle(right, align=2, size=size)
+	MergeHoriz(tleft, tright, -1)
+	AddBorders(0, 2, 0, 2)
+}
+
+function MakeFrameNumberClip(clip c, int frames)
+{
+	width = fontsize * 5 / 2 + 1
+	halved = (c.Width - width) / 2
+	ShowFrameNumber(BlankClip(c, frames, width=width, height=fontsize + 1), size=fontsize)
+	Crop(0, 5, -0, -0)
+	AddBorders(halved, 0, halved, 4)
+	AddBorders(0, 2, 0, 2)
+}
+
+function AdjustClip(clip c, int offset)
+{
+	# set up your padding and resizing here
+	PointResize(c, c.Width * 2, c.Height * 2)
+	AddBorders(64 + offset, 0, 64 - offset, 0)
+	MergeVert(MakeFrameNumberClip(last.FrameCount), last, 2)
+	AddBorders(0, 16 - 2, 0, 16)
+}
+
+# http://tasvideos.org/485M.html
+global old_name = "phil"
+global old_date = "2006-02-25"
+global old_frames = 32248
+global old_time = "08:57.47"
+global old_comment = "http://tasvideos.org/985S.html"
+AviSource("phil5-ddragon-again.avi")+\
+AviSource("phil5-ddragon-again_part2.avi")+\
+AviSource("phil5-ddragon-again_part3.avi")
+Trim(0, old_frames + 1636)
+#ShowFrameNumber(scroll=true)
+AdjustClip(0)#-48)
+global old = last
+
+# http://tasvideos.org/3211M.html
+global new_name = "alyosha"
+global new_date = "2016-08-28"
+global new_frames = 31869
+global new_time = "08:50.28"
+global new_comment = "http://tasvideos.org/5207S.html"
+AviSource("alyosha-doubledragon-again.avi")+\
+AviSource("alyosha-doubledragon-again_part2.avi")+\
+AviSource("alyosha-doubledragon-again_part3.avi")
+Trim(0, new_frames + 1636)
+#ShowFrameNumber(scroll=true)
+AdjustClip(0)#48)
+global new = last
+
+# compare by slice
+function x(int oldStart, int oldEnd, int newStart, int newEnd, string title)
+{
+	left = Trim(old, oldStart, oldEnd)
+	right = Trim(new, newStart, newEnd)
+	frames = max(left.FrameCount, right.FrameCount)
+	fc = MakeFrameNumberClip(left, frames)
+	TextHoriz(left, frames, old_name + " (" + old_date + ")", new_name + " (" + new_date + ")")
+	MergeVert(last, TextHoriz(left, frames, String(old_frames) + " frames (" + old_time + ")", string(new_frames) + " frames (" + new_time + ")"), -1)
+	MergeVert(last, TextHoriz(left, frames, old_comment, new_comment), -1)
+	MergeVert(last, Cmp(left, right), 2)
+	MergeVert(last, TextHoriz(left, frames, title, title), 1)
+	MergeVert(last, TextHoriz(left, frames, "in " + String(left.FrameCount) + " frames", "in " + String(Right.FrameCount) + " frames"), 1)
+	MergeVert(last, MergeHoriz(fc, fc, -1), 1)
+}
+
+# compare by split (start is last split)
+global prevOldSplit = 0
+global prevNewSplit = 0
+function s(int oldSplit, int newSplit, string title)
+{
+	ot = prevOldSplit
+	nt = prevNewSplit
+	global prevOldSplit = oldSplit + 1
+	global prevNewSplit = newSplit + 1
+	return x(ot, oldSplit, nt, newSplit, title)
+}
+
+# TODO: frames gained/lost in corner per file
+
+s( 1557, 1547, "first screen scroll")+\
+s( 1869, 1862, "first door opening")+\
+s( 2123, 2143, "second screen scroll")+\
+s( 3041, 3067, "third screen scroll")+\
+s( 3973, 4017, "door entered")+\
+s( 4729, 4817, "mission completed")+\
+s( 5943, 6059, "first screen scroll")+\
+s( 6489, 6601, "background visible again")+\
+s( 7118, 7229, "second screen scroll")+\
+s( 7604, 7713, "top of first ladder")+\
+s( 7988, 8094, "top of second ladder")+\
+s( 8316, 8416, "top of third ladder")+\
+s( 8649, 8749, "first door opening")+\
+s( 9291, 9393, "mission completed")+\
+s(10515,10611, "first screen scroll")+\
+s(11695,11747, "second screen scroll")+\
+s(12514,12581, "third screen scroll")+\
+s(13412,13543, "fourth screen scroll")+\
+s(14588,14773, "door entered")+\
+s(15369,15548, "platformer begin")+\
+s(15764,15933, "platformer finished")+\
+s(16087,16256, "first door opening")+\
+s(16941,17111, "door entered")+\
+s(17008,17179, "loaded")+\
+s(17794,17984, "first screen scroll")+\
+s(18793,18983, "black screen")+\
+s(19398,19608, "boss defeated")+\
+s(20776,20994, "mission completed")+\
+s(22572,22804, "first screen scroll")+\
+s(23183,23400, "climbed wall")+\
+s(24076,24398, "black screen")+\
+s(24326,24642, "top of first ladder")+\
+s(24788,25108, "top of second ladder")+\
+s(25606,25917, "top of third ladder")+\
+s(26147,26446, "top of fourth ladder")+\
+s(26283,26642, "black screen")+\
+s(27623,27788, "first screen scroll")+\
+s(27951,28118, "first door opening")+\
+s(28800,28585, "second door opening")+\
+s(29492,29152, "third door opening")+\
+s(29660,29320, "fourth door opening")+\
+s(29944,29545, "fifth door opening")+\
+s(30683,30290, "sixth door opening")+\
+s(old_frames,new_frames, "end of input")+\
+s(    0,    0, "end of game")
+AddBorders(0, 16, 0, 16)