user: You are a structured reasoning expert tasked with solving problems step by step. 
You first think about the reasoning process in the mind and then provide the answer. The reasoning process and answer should be enclosed within <think> </think> and <answer> </answer> tags, respectively, i.e., <think> reasoning process here </think> <answer> answer here </answer>. 
Given a question and the associated knowledge graph triplets (entity, relation, entity), you are asked to answer the question with these triplets and your own knowledge. 
You can break down the original question into several sub-questions and explore the given knowledge graph to solve them step-by-step. If there are multiple possible answers, choose one as the final answer. 
After thinking, when you finally reach a conclusion, clearly state the answer within <answer> </answer> tags, i.e., <answer> answer here </answer>. 
Question: the computer games korsakovia uses a video game engine developed by what video game engine developer? 
Knowledge Triplets: Yousei, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Nuclear Dawn
Heist, cvg.computer_videogame.platforms, Microsoft Windows
Half-Life: Source, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, Vindictus
Source Engine, cvg.computer_game_engine.used_for_computer_games, Fistful of Frags
Jailbreak: Source, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, The DinoHunters
Source Engine, cvg.computer_game_engine.used_for_computer_games, E.Y.E.: Divine Cybermancy
Sam & Max Hit the Road, cvg.computer_videogame.platforms, Microsoft Windows
Natural Selection 2, cvg.computer_videogame.uses_game_engine, Source Engine
Postal III, cvg.computer_videogame.uses_game_engine, Source Engine
Blood Omen 2, cvg.computer_videogame.platforms, Microsoft Windows
Hybrid, cvg.computer_videogame.uses_game_engine, Source Engine
Counter-Strike: Source, cvg.computer_videogame.uses_game_engine, Source Engine
Korsakovia, base.wikipedia_infobox.video_game.platforms, Microsoft Windows
Korsakovia, base.wikipedia_infobox.video_game.developer, The Chinese Room
Source Engine, cvg.computer_game_engine.used_for_computer_games, Half-Life: Source
Day of Defeat: Source, cvg.computer_videogame.uses_game_engine, Source Engine
Korsakovia, cvg.computer_videogame.release_date, 2009
Dogfights: The Game, cvg.computer_videogame.uses_game_engine, Source Engine
Korsakovia, cvg.computer_videogame.uses_game_engine, Source Engine
Half-Life 2: Episode One, cvg.computer_videogame.uses_game_engine, Source Engine
The Crossing, cvg.computer_videogame.uses_game_engine, Source Engine
Zombie Panic! Source, cvg.computer_videogame.uses_game_engine, Source Engine
Nuclear Dawn, cvg.computer_videogame.uses_game_engine, Source Engine
Dear Esther, base.wikipedia_infobox.video_game.developer, The Chinese Room
Left 4 Dead, cvg.computer_videogame.uses_game_engine, Source Engine
Blade Symphony, cvg.computer_videogame.uses_game_engine, Source Engine
Zeno Clash, cvg.computer_videogame.uses_game_engine, Source Engine
Left 4 Dead 2, cvg.computer_videogame.uses_game_engine, Source Engine
Korsakovia, cvg.computer_videogame.gameplay_modes, Single-player video game
Source Engine, cvg.computer_game_engine.used_for_computer_games, Half-Life 2: Deathmatch
The Sims, cvg.computer_videogame.platforms, Microsoft Windows
Portal, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, Vampire: The Masquerade – Bloodlines
Alien Swarm: Infested, cvg.computer_videogame.uses_game_engine, Source Engine
Total Annihilation, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Kuma\War
Source Engine, cvg.computer_game_engine.used_for_computer_games, Blade Symphony
Source Engine, cvg.computer_game_engine.used_for_computer_games, GoldenEye: Source
Kuma\War, cvg.computer_videogame.uses_game_engine, Source Engine
Yo Frankie!, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Half-Life 2
Eternal Silence, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine_developer.computer_game_engines_developed, Valve Corporation
Source Engine, cvg.computer_game_engine.used_for_computer_games, Alien Swarm
Half-Life 2: Episode Two, cvg.computer_videogame.uses_game_engine, Source Engine
The Elder Scrolls V: Skyrim – Dragonborn, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Fortress Forever
The Ship, cvg.computer_videogame.uses_game_engine, Source Engine
Dark Sector, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Shootout! The Game
Scivelation, cvg.computer_videogame.uses_game_engine, Source Engine
Vampire: The Masquerade – Bloodlines, cvg.computer_videogame.uses_game_engine, Source Engine
Shootout! The Game, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, Left 4 Dead
The Curse of Monkey Island, cvg.computer_videogame.platforms, Microsoft Windows
Civilization IV, cvg.computer_videogame.platforms, Microsoft Windows
The Kill Point Game, cvg.computer_videogame.uses_game_engine, Source Engine
Dear Esther, cvg.computer_videogame.developer, The Chinese Room
The Stanley Parable, cvg.computer_videogame.uses_game_engine, Source Engine
Dear Esther, cvg.computer_videogame.uses_game_engine, Source Engine
Armadillo Run, cvg.computer_videogame.platforms, Microsoft Windows
Fistful of Frags, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, g.1ylhlkqr9
Source Engine, cvg.computer_game_engine.used_for_computer_games, Dystopia
Source Engine, cvg.computer_game_engine.used_for_computer_games, The Ship
UEFA Euro 2012, cvg.computer_videogame.platforms, Microsoft Windows
Valve Corporation, cvg.computer_game_engine_developer.computer_game_engines_developed, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, Insurgency: Modern Infantry Combat
Firearms: Source, cvg.computer_videogame.uses_game_engine, Source Engine
City Bus Simulator, cvg.computer_videogame.platforms, Microsoft Windows
Amnesia: A Machine for Pigs, base.wikipedia_infobox.video_game.developer, The Chinese Room
Tactical Intervention, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, Zeno Clash
Source Engine, cvg.computer_game_engine.used_for_computer_games, Bloody Good Time
GoldenEye: Source, cvg.computer_videogame.uses_game_engine, Source Engine
Assassin's Creed: Brotherhood, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Mabinogi
FIFA Manager 06, cvg.computer_videogame.platforms, Microsoft Windows
BioShock Infinite, cvg.computer_videogame.platforms, Microsoft Windows
Mass Effect 2: Overlord, cvg.computer_videogame.platforms, Microsoft Windows
Medal of Honor: Warfighter, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Aperture Tag
Source Engine, cvg.computer_game_engine.used_for_computer_games, g.121_4qvh
Half-Life 2: Survivor, cvg.computer_videogame.uses_game_engine, Source Engine
DoomRL, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Portal
Prime, cvg.computer_videogame.uses_game_engine, Source Engine
Call of Duty: Black Ops II, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.developer, Valve Corporation
Source Engine, cvg.computer_game_engine.used_for_computer_games, The Crossing
The Dig, cvg.computer_videogame.platforms, Microsoft Windows
Path of Exile, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Portal 2
Warframe, cvg.computer_videogame.platforms, Microsoft Windows
TractorSource, cvg.computer_videogame.uses_game_engine, Source Engine
Civilization, cvg.computer_videogame.platforms, Microsoft Windows
Team Fortress 2, cvg.computer_videogame.uses_game_engine, Source Engine
The Next Big Thing, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Half-Life 2: Episode Two
Everybody's Gone to the Rapture, base.wikipedia_infobox.video_game.developer, The Chinese Room
Lost Saga, cvg.computer_videogame.platforms, Microsoft Windows
Total War: Rome II, cvg.computer_videogame.platforms, Microsoft Windows
Counter-Strike Online, cvg.computer_videogame.uses_game_engine, Source Engine
Titanfall, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, Eternal Silence
SiN Episodes, cvg.computer_videogame.uses_game_engine, Source Engine
Half-Life 2: Lost Coast, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, Half-Life 2: Lost Coast
Source Engine, cvg.computer_game_engine.used_for_computer_games, They Hunger: Lost Souls
Source Engine, cvg.computer_game_engine.used_for_computer_games, Half-Life 2: Survivor
Source Engine, cvg.computer_game_engine.used_for_computer_games, Prime
Source Engine, cvg.computer_game_engine.used_for_computer_games, Korsakovia
Half-Life 2, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, Tactical Intervention
Source Engine, cvg.computer_game_engine.used_for_computer_games, Half-Life: Decay
Dying Light, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Postal III
Source Engine, cvg.computer_game_engine.used_for_computer_games, Natural Selection 2
Source Engine, cvg.computer_game_engine.used_for_computer_games, Left 4 Dead 2
The DinoHunters, cvg.computer_videogame.uses_game_engine, Source Engine
SourceForts, cvg.computer_videogame.uses_game_engine, Source Engine
The Gallery: Six Elements, cvg.computer_videogame.platforms, Microsoft Windows
Yesterday, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, NeoTokyo
Mabinogi, cvg.computer_videogame.uses_game_engine, Source Engine
Pirates, Vikings and Knights II, cvg.computer_videogame.uses_game_engine, Source Engine
007: Quantum of Solace, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Dota 2
Tiny Brains, cvg.computer_videogame.platforms, Microsoft Windows
RollerCoaster Tycoon 3, cvg.computer_videogame.platforms, Microsoft Windows
Counter-Strike: Global Offensive, cvg.computer_videogame.uses_game_engine, Source Engine
Sherlock Holmes: Crimes & Punishments, cvg.computer_videogame.platforms, Microsoft Windows
Half-Life 2: Capture the Flag, cvg.computer_videogame.uses_game_engine, Source Engine
Half-Life 2: Episode Three, cvg.computer_videogame.uses_game_engine, Source Engine
Inquisitor, cvg.computer_videogame.platforms, Microsoft Windows
Dino D-Day, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, SourceForts
Source Engine, cvg.computer_game_engine.used_for_computer_games, Iron Grip: The Oppression
Pro Evolution Soccer 2012, cvg.computer_videogame.platforms, Microsoft Windows
NeoTokyo, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, Dogfights: The Game
Daylight, cvg.computer_videogame.platforms, Microsoft Windows
Infinite Crisis, cvg.computer_videogame.platforms, Microsoft Windows
Deep 6, cvg.computer_videogame.uses_game_engine, Source Engine
10000000, cvg.computer_videogame.platforms, Microsoft Windows
Empires, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, Alien Swarm: Infested
Half-Life 2: Deathmatch, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, Dark Messiah of Might and Magic
The Crew, cvg.computer_videogame.platforms, Microsoft Windows
Escape from Monkey Island, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Counter-Strike Online
E.Y.E.: Divine Cybermancy, cvg.computer_videogame.uses_game_engine, Source Engine
Black Mesa, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, Empires
Alter Ego, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Team Fortress 2
No More Room in Hell, cvg.computer_videogame.uses_game_engine, Source Engine
Long Live the Queen, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Dear Esther
Pro Evolution Soccer 2010, cvg.computer_videogame.platforms, Microsoft Windows
Contagion, cvg.computer_videogame.uses_game_engine, Source Engine
Alien Swarm, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, The Orange Box
Source Engine, cvg.computer_game_engine.used_for_computer_games, SiN Episodes
Portal 2, cvg.computer_videogame.uses_game_engine, Source Engine
Duke Nukem Forever, cvg.computer_videogame.platforms, Microsoft Windows
The Chinese Room, cvg.cvg_developer.games_developed, Dear Esther
Euro Truck Simulator 2, cvg.computer_videogame.platforms, Microsoft Windows
The Last Express, cvg.computer_videogame.platforms, Microsoft Windows
Insurgency: Modern Infantry Combat, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, Half-Life 2: Episode Three
Source Engine, cvg.computer_game_engine.used_for_computer_games, Dino D-Day
Harpoon, cvg.computer_videogame.platforms, Microsoft Windows
Garry's Mod, cvg.computer_videogame.uses_game_engine, Source Engine
Resistance and Liberation, cvg.computer_videogame.uses_game_engine, Source Engine
g.121_4qvh, cvg.computer_videogame.uses_game_engine, Source Engine
Tony Hawk's Underground 2, cvg.computer_videogame.platforms, Microsoft Windows
Isomer, cvg.computer_videogame.platforms, Microsoft Windows
World of Tanks, cvg.computer_videogame.platforms, Microsoft Windows
Strider, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, No More Room in Hell
F1 2011, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Garry's Mod
League of Legends, cvg.computer_videogame.platforms, Microsoft Windows
Actua Ice Hockey, cvg.computer_videogame.platforms, Microsoft Windows
Cube World, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Twilight War: After the Fall
Cypher, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Firearms: Source
Full Throttle, cvg.computer_videogame.platforms, Microsoft Windows
g.1ylhlkqr9, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, Scivelation
Half-Life: Decay, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, Day of Defeat: Source
They Hunger: Lost Souls, cvg.computer_videogame.uses_game_engine, Source Engine
Contrast, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Zombie Panic! Source
SteamBand, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Black Mesa
Source Engine, cvg.computer_game_engine.used_for_computer_games, Jailbreak: Source
Chameleon, cvg.computer_videogame.platforms, Microsoft Windows
LambdaRogue, cvg.computer_videogame.platforms, Microsoft Windows
Dark Messiah of Might and Magic, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, The Kill Point Game
Fortress Forever, cvg.computer_videogame.uses_game_engine, Source Engine
Bless, cvg.computer_videogame.platforms, Microsoft Windows
Aperture Tag, cvg.computer_videogame.uses_game_engine, Source Engine
Bloody Good Time, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, Titanfall
Single-player video game, cvg.gameplay_mode.games_with_this_mode, Korsakovia
Source Engine, cvg.computer_game_engine.used_for_computer_games, Pirates, Vikings and Knights II
Hotline Miami, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Half-Life 2: Capture the Flag
Vindictus, cvg.computer_videogame.uses_game_engine, Source Engine
Twilight War: After the Fall, cvg.computer_videogame.uses_game_engine, Source Engine
Factorio, base.wikipedia_infobox.video_game.developer, The Chinese Room
Bad Piggies, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, The Stanley Parable
Source Engine, cvg.computer_game_engine.used_for_computer_games, Counter-Strike: Global Offensive
Source Engine, cvg.computer_game_engine.used_for_computer_games, Resistance and Liberation
Battle Cry of Freedom, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Deep 6
Source Engine, cvg.computer_game_engine.used_for_computer_games, Half-Life 2: Episode One
Dystopia, cvg.computer_videogame.uses_game_engine, Source Engine
Source Engine, cvg.computer_game_engine.used_for_computer_games, Counter-Strike: Source
Borderlands 2, cvg.computer_videogame.platforms, Microsoft Windows
Source Engine, cvg.computer_game_engine.used_for_computer_games, Hybrid
Iron Grip: The Oppression, cvg.computer_videogame.uses_game_engine, Source Engine
Spelunky, cvg.computer_videogame.platforms, Microsoft Windows
Dota 2, cvg.computer_videogame.uses_game_engine, Source Engine
Grim Fandango, cvg.computer_videogame.platforms, Microsoft Windows
The Orange Box, cvg.computer_videogame.uses_game_engine, Source Engine
Dear Esther, cvg.computer_videogame.publisher, The Chinese Room
Source Engine, cvg.computer_game_engine.used_for_computer_games, Contagion
Source Engine, cvg.computer_game_engine.used_for_computer_games, TractorSource
Microsoft Windows, computer.software.developer, Microsoft Corporation

Answer: Valve Corporation