You can copy in the good ones from the LD13 theme list or add new themes! As a general rule, try to avoid themes that either require specific cultural knowledge (including sports), or impose implementation limitations (like “2-bit color”). Please use alphabetical ordering so it's easy to see if a certain theme is already added.

Themes go here:

• Achievements
• Advancing Wall of Doom
• All Your Base
• Animals
• Any Fiction 100 years + old
• And what now?

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• April the Twentieth
• Astrobiology
• Attraction
• Autobiography
• Bicycle
• Board Game
• Body parts
• Bosses
• Breaking the rules
• Cactus
• Cards
• Chain reaction
• Circuits
• Collecting
• Cooperation
• Conspiracy
• Control
• Corpse Stacking
• Coffee
• Cryogenics/Cryonics
• Cyberspace
• Dark Ages
• Data Collection and Analysis
• Death
• Defense
• Depression
• Distorted perception
• Don't think, do.
• Drums and drumming.
• Economics
• Educational (If kid's can learn the names of all hundred-dozen-some-odd Pokemon, why can't they learn about something real?)
• Epidemic
• Ergonomics
• Eroticism
• Explosions
• Extremes
• Evil, defeat the lone hero!
• Evolution
• Fail to win
• Ferrets
• Flat
• Flora and Fauna
• Fluoride
• Flying
• Four Seasons.
• Game of life ( as in "this", but with broader interpretation)
• Game within a game
• Genetic
• Geometry
• Giant Naked Men (Dr. Manhattan?) [Or, indeed, any other giant naked men that may come to mind]
• Gladiators
• Globe
• God(s) (or religion)
• Government Conspiracy
• Gravity
• Greedy
• Gulliver's Travels
• Help the helpless
• HG Wells Story
• High
• Hold the Line
• Invasive advertisements
• Infinity
• Irony
• I accidentally the whole thing
• Jules Verne Story
• King
• Kittens
• Lasers and Mirrors
• Laser Cats
• Layers
• Leprechauns
• Linguistics/Translation/Interpretation
• Lots of different endings
• Love
• Meat vs. Vegetables
• Microscopic World
• Mirror
• Mons
• Mountain Goats
• Multiple types of health meters
• Music
• Nachos
• Nintendo Hard
• Non euclidean space ←– Noooooooo!!!! I hate hyperbolic geometry!
• Non Sequitur
• Nude beach management
• One Hit Point Wonder
• One way out
• Online high scores
• Opposites
• Over-complication
• Over-simplification
• Overlords
• Paper
• Perpetual motion
• Player's actions coming back to bite him/her in the keister
• Pollution
• Procedural Generation
• Psychedelic
• Psychology
• Psychonauts
• Purposed Play (playing the game aides productivity)
• Quanta
• Quantum physics
• Queues
• Radiation
• Rain
• Randomness (never the same twice)
• Reality TV
• Recursion, specifically: "Yo dawg..."
• Red Herring
• Reflection
• Relationships
• Renaissance
• Reverse Engineering
• Revolt
• Rewind
• Robot
• Rogue Nanobots
• Role Reversal
• Roman Empire
• Roundabout methods
• Sandbox
• Scheme
• Science Fiction
• Sex
• Short Complete Story
• Sickeningly Cute
• Single Enemy
• Simplexity (complexity emerging from a simple design)
• Sniping
• Source of reality
• Spicy
• Spinning
• Squids
• Springs
• Social interaction
• Stab the Pope
• Synesthesia
• Taxes
• Time traveling
• To be played in a public place
• Toaster
• Toys
• Track
• Transport
• Turn-based strategy
• Turbo Hyper Ultra Mega Laser Ninjas 3000
• Two versions of the same thing
• Tycoon
• Universal
• User designed entities(Machines/Gadgets/Organisms)
• Versus
• Very Short Games
• Water Pressure
• Werewolves
• What I did last weekend… the game!
• Wikipedia (the site somehow plays into the game's design)
• Winamp
• Winter
• Words
• Wormholes
• Xylophone
• Xenophobia
• Yetis
• Your Mother
• Zero Repetition
• Zombies
• Zapping
• WORMS AND ZOMBIES ←- dude, that is *not* alphabetical order ^^
• …

(let's not use these again for a while)

• LD13: Roads
• LD12: The Tower
• LD11: Minimalist
• LD10.5: Weird/Unexpected/Surprise
• LD10: Chain Reaction
• LD9: Build the level you play
• LD8.5: Moon, Anti-Text
• LD8: Swarms
• LD7: Growth
• LD6: Light and Darkness
• LD5: Random
• LD4: Infection
• LD3: Preparation
• LD2: Construction/Destruction (Minor Theme: Sheep)
• LD1: Guardian
• LD0: Indirect Interaction

• Mini LD #8 (Hamumu - March 09): Mash-up
• Mini LD #7 (Philhassey - February 09): Cryptozoology
• Mini LD #6 (Matrin - January 09): Monochrome
• Mini LD #5 (Hamumu - November 08): Cover
• Mini LD #4 (Eugman - October 08): MSpaint: Best Level Editor Ever
• Mini LD #3 (PoV - September 08): Tool
• Mini LD #2 (GirlFlash - July 08): The game of the movie (Minor Theme: Unicorn)
• Mini LD #1 (Hamumu - June 08): Versus (Two extremely famous or iconic characters)

• PW7: The length of a piece of string
• PW6: Robot
• PW5: Twisted
• PW4: The only way is up
• PW3: The Disappearing Act
• PW2: It runs on steam!
• PW1: Power

• RWE1: Pirates vs. Zombies
• RWE2: Opposites

• 72HGDC #8 Nov '06: Magnets
• 72HGDC #7 Jul '06: Retro
• 72HGDC #6 Mar '06: Magic
• 72HGDC #5 Jul '05: Horror
• 72HGDC #4 Dec '04: Swappable Parts/Customize?
• 72HGDC #3 Jun '04: Pirates
• 72HGDC #2 Jan '04: Food
• 72HGDC #1 Jul '03: Mindless violence

• FGDC4: Ball Physics
• FGDC3: Replay
• FGDC2: Grow
• FGDC1: Point & Click