Get the Portal The Flash Version Mappack off WP (45mb)
IMPORTANT:
This mappack requires both Portal and Half Life 2 to be owned and installed in order to work.
Just drop the content of the file (the 4 folders) in ValveSteamsteamapps/youraccountname/portalportal and replace files if needed.
Then load the game, go to Bonus maps and Load the the Mappack from the list.
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