Engine: Dragon's Keep engine
Written in Applesoft Basic by Al Lowe in 1982, this very basic engine for non-animated games (but quite advanced for its time according to Al) was built for his very first game, Dragon's Keep, which he first published under his own start-up software company, Sunnyside Soft.
It allows games to be played with just 2 controls: the space bar and enter key. The space bar is used to select one of up to three options available to the player at the bottom of the screen and the enter key is used to execute the selected option. Options are always a direction the player can go to (leading to the display of a new screen) or an action on screen. Additional controls allowed to enable or disable sound or to display a sort of inventory screen to track progress in the game.
After Sierra absorbed Sunnyside Soft, several more games, all programmed by Al Lowe, used the same engine. Due to its simple use, these were all games for young children. It was used for Troll's Tale (which had the same find-and-retrieve concept of Dragon's Keep), Gelfling Adventure (spin-off of Hi-Res Adventure #6 which itself used a text parser) and lastly Winnie the Pooh In The Hundred Acre Wood.
With the introduction of Sierra's animated adventure games through the AGI engine in 1984, the Dragon's Keep engine became obsolete and was no longer used.