The N-Screen contents is a kind of emerging technologies to make a new user-experience by integrating multiple devices like smart TVs, personal computers, and smartphones. In the paper, we characterize game design issues of N-Screen based game with smart TV and smartphone and describe the game design issues of 「Beaver Rising」as its case study.「Beaver Rising」is the N-Screen game which developed by our team ans its' game play is similar with a classic game, called「Snake」but it can be played on a smart TV screen while players can control their own beaver characters with their smartphones. We first give a survey of N-Screen games to characterize their properties in the paper. Then, we describe the game play, game design architecture, and user experience of the game,「Beaver Rising」as its case study. Finally, we propose three new properties to make an effective N-screen game with a smart TV and smartphons. The paper will contribute to provide am effective game design guideline when we make a N-screen based game with a smart TV and smartphones.