diff --git a/SOURCES.md b/SOURCES.md
index 9e527a0..6851c4e 100644
--- a/SOURCES.md
+++ b/SOURCES.md
@@ -8,7 +8,7 @@ Some of the assets are used without proper licenses. We aim to have fully licens
 Backgrounds
 -----------
 
-1. Title: Original picrute found on the Wikipedia article for Cambridge
+1. Title: "Motus Glacies." Contributed by Daniel "Explo" McCarthy.
 
 1. *Gameplay level 0: "Quantum foam." Alex Sukontsev. https://www.flickr.com/photos/control9/14957509814/
 2. *Gameplay level 1: No name. http://www.onekind.tv/univision-mqb/q5mqh5brlvuuj2nhdx7ch7eum183uu
diff --git a/load/graphics.lua b/load/graphics.lua
index 00d5d4b..a0525b0 100644
--- a/load/graphics.lua
+++ b/load/graphics.lua
@@ -1,27 +1,27 @@
 backgrounds = {
-	[0] = love.graphics.newImage("res/backgrounds/0.png"),
-	love.graphics.newImage("res/backgrounds/100.png"),
-	love.graphics.newImage("res/backgrounds/200.png"),
-	love.graphics.newImage("res/backgrounds/300.png"),
-	love.graphics.newImage("res/backgrounds/400.png"),
-	love.graphics.newImage("res/backgrounds/500.png"),
-	love.graphics.newImage("res/backgrounds/600.png"),
-	love.graphics.newImage("res/backgrounds/700.png"),
-	love.graphics.newImage("res/backgrounds/800.png"),
-	love.graphics.newImage("res/backgrounds/900.png"),
-	love.graphics.newImage("res/backgrounds/1000.png"),
-	love.graphics.newImage("res/backgrounds/1100.png"),
-	love.graphics.newImage("res/backgrounds/1200.png"),
-	love.graphics.newImage("res/backgrounds/1300.png"),
-	love.graphics.newImage("res/backgrounds/1400.png"),
-	love.graphics.newImage("res/backgrounds/1500.png"),
-	love.graphics.newImage("res/backgrounds/1600.png"),
-	love.graphics.newImage("res/backgrounds/1700.png"),
-	love.graphics.newImage("res/backgrounds/1800.png"),
-	love.graphics.newImage("res/backgrounds/1900.png"),
-	title = love.graphics.newImage("res/backgrounds/title.png"),
-	input_config = love.graphics.newImage("res/backgrounds/options-input.png"),
-	game_config = love.graphics.newImage("res/backgrounds/options-game.png"),
+	[0] = love.graphics.newImage("res/backgrounds/0-quantum-foam.png"),
+	love.graphics.newImage("res/backgrounds/100-big-bang.png"),
+	love.graphics.newImage("res/backgrounds/200-spiral-galaxy.png"),
+	love.graphics.newImage("res/backgrounds/300-sun-and-dust.png"),
+	love.graphics.newImage("res/backgrounds/400-earth-and-moon.png"),
+	love.graphics.newImage("res/backgrounds/500-cambrian-explosion.png"),
+	love.graphics.newImage("res/backgrounds/600-dinosaurs.png"),
+	love.graphics.newImage("res/backgrounds/700-asteroid.png"),
+	love.graphics.newImage("res/backgrounds/800-human-fire.png"),
+	love.graphics.newImage("res/backgrounds/900-early-civilization.png"),
+	love.graphics.newImage("res/backgrounds/1000-vikings.png"),
+	love.graphics.newImage("res/backgrounds/1100-crusades.png"),
+	love.graphics.newImage("res/backgrounds/1200-genghis-khan.png"),
+	love.graphics.newImage("res/backgrounds/1300-black-death.png"),
+	love.graphics.newImage("res/backgrounds/1400-columbus-discovery.png"),
+	love.graphics.newImage("res/backgrounds/1500-aztecas.png"),
+	love.graphics.newImage("res/backgrounds/1600-telescope.png"),
+	love.graphics.newImage("res/backgrounds/1700-american-revolution.png"),
+	love.graphics.newImage("res/backgrounds/1800-railways.png"),
+	love.graphics.newImage("res/backgrounds/1900-world-wide-web.png"),
+	title = love.graphics.newImage("res/backgrounds/title_v0.1.png"),
+	input_config = love.graphics.newImage("res/backgrounds/options-pcb.png"),
+	game_config = love.graphics.newImage("res/backgrounds/options-gears.png"),
 }
 
 blocks = {
diff --git a/res/backgrounds/0.png b/res/backgrounds/0-quantum-foam.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/0.png
rename to res/backgrounds/0-quantum-foam.png
diff --git a/res/backgrounds/100.png b/res/backgrounds/100-big-bang.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/100.png
rename to res/backgrounds/100-big-bang.png
diff --git a/res/backgrounds/1000.png b/res/backgrounds/1000-vikings.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/1000.png
rename to res/backgrounds/1000-vikings.png
diff --git a/res/backgrounds/1100.png b/res/backgrounds/1100-crusades.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/1100.png
rename to res/backgrounds/1100-crusades.png
diff --git a/res/backgrounds/1200.png b/res/backgrounds/1200-genghis-khan.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/1200.png
rename to res/backgrounds/1200-genghis-khan.png
diff --git a/res/backgrounds/1300.png b/res/backgrounds/1300-black-death.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/1300.png
rename to res/backgrounds/1300-black-death.png
diff --git a/res/backgrounds/1400.png b/res/backgrounds/1400-columbus-discovery.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/1400.png
rename to res/backgrounds/1400-columbus-discovery.png
diff --git a/res/backgrounds/1500.png b/res/backgrounds/1500-aztecas.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/1500.png
rename to res/backgrounds/1500-aztecas.png
diff --git a/res/backgrounds/1600.png b/res/backgrounds/1600-telescope.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/1600.png
rename to res/backgrounds/1600-telescope.png
diff --git a/res/backgrounds/1700.png b/res/backgrounds/1700-american-revolution.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/1700.png
rename to res/backgrounds/1700-american-revolution.png
diff --git a/res/backgrounds/1800.png b/res/backgrounds/1800-railways.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/1800.png
rename to res/backgrounds/1800-railways.png
diff --git a/res/backgrounds/1900.png b/res/backgrounds/1900-world-wide-web.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/1900.png
rename to res/backgrounds/1900-world-wide-web.png
diff --git a/res/backgrounds/200.png b/res/backgrounds/200-spiral-galaxy.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/200.png
rename to res/backgrounds/200-spiral-galaxy.png
diff --git a/res/backgrounds/300.png b/res/backgrounds/300-sun-and-dust.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/300.png
rename to res/backgrounds/300-sun-and-dust.png
diff --git a/res/backgrounds/400.png b/res/backgrounds/400-earth-and-moon.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/400.png
rename to res/backgrounds/400-earth-and-moon.png
diff --git a/res/backgrounds/500.png b/res/backgrounds/500-cambrian-explosion.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/500.png
rename to res/backgrounds/500-cambrian-explosion.png
diff --git a/res/backgrounds/600.png b/res/backgrounds/600-dinosaurs.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/600.png
rename to res/backgrounds/600-dinosaurs.png
diff --git a/res/backgrounds/700.png b/res/backgrounds/700-asteroid.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/700.png
rename to res/backgrounds/700-asteroid.png
diff --git a/res/backgrounds/800.png b/res/backgrounds/800-human-fire.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/800.png
rename to res/backgrounds/800-human-fire.png
diff --git a/res/backgrounds/900.png b/res/backgrounds/900-early-civilization.png
old mode 100644
new mode 100755
similarity index 100%
rename from res/backgrounds/900.png
rename to res/backgrounds/900-early-civilization.png
diff --git a/res/backgrounds/options-game.png b/res/backgrounds/options-gears.png
similarity index 100%
rename from res/backgrounds/options-game.png
rename to res/backgrounds/options-gears.png
diff --git a/res/backgrounds/options-input.png b/res/backgrounds/options-pcb.png
similarity index 100%
rename from res/backgrounds/options-input.png
rename to res/backgrounds/options-pcb.png
diff --git a/res/backgrounds/title.png b/res/backgrounds/title_v0.1.png
similarity index 100%
rename from res/backgrounds/title.png
rename to res/backgrounds/title_v0.1.png
diff --git a/res/se/bottom.wav b/res/se/bottom.wav
index 9b23bf5..1a66150 100644
Binary files a/res/se/bottom.wav and b/res/se/bottom.wav differ
diff --git a/res/se/cursor.wav b/res/se/cursor.wav
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diff --git a/res/se/cursor_lr.wav b/res/se/cursor_lr.wav
index 15d581d..9e7245e 100644
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diff --git a/res/se/fall.wav b/res/se/fall.wav
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