One approach to teaching game design to students with a wide variety of disciplinary backgrounds is through team game projects that span multiple weeks, up to an entire term. However, open-ended, creative projects introduce a gamut of challenges to novice programmers. My goal is to assist game design students with the planning stage of their projects through a software tool. In this document I describe an iterative design process towards this support. First, I collected data through three course interventions and student interviews, and learned students had difficulty expressing their creative vision and connecting the game mechanics to the intended player experience. These findings influenced the construction of a tool, and I introduce the Game Mechanic Mechanic tool for project planning which includes a game mechanic browser featuring mechanics drawn from a corpus of PuzzleScript games, and a sequence of questions for students to directly connect player experience goals to the game mechanics they select. I provide a classroom evaluation for the tool through scaffolding the planning process for student game projects, and found that providing example mechanics and prompting the student to articulate the intended player experience assists the student in better connecting design decisions about game mechanics and connecting them to the intended gameplay experience. I also introduce Mechanic Playgrounds, interactive environments where students can mix and match example mechanics and generate complimentary mechanics, showing that generated mechanics which align with existing PuzzleScript rules can provide examples which expose sensical, usable, and inspirational aspects of the generative PuzzleScript space by focusing on specific properties of PuzzleScript rules. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]