The purpose of this multiple-paper dissertation is to design a digital game and stealth assessments within the game to assess young second language learners' Chinese reading proficiency. In Chapter 2 (Paper 1), I describe the game designed for this dissertation and how it was implemented in a dual language immersion classroom. This study found that the digital game and in-class implementation led to significant vocabulary and reading comprehension gains. Further, seven types of support that students needed while playing the game were identified. In Chapter 3 (Paper 2), I describe how educational data mining approaches, and more specifically, how data-driven explorations, can provide insight into how players interact with the game and further how those interactions relate to proficiency and learning. In this study, I identify time on task and use of an in-game glossing tool as important indicators for learning. In addition, four subgroups of students were identified based on their gameplay styles. Finally, in Chapter 4 (Paper 3), I describe how stealth assessments were designed and validated within the game. This study found that the stealth assessments were significantly correlated with two external measures of reading comprehension. [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.]