To date, applying what is known about child development to educational app design has been minimally studied and rarely tested. Using developmental and learning sciences research (e.g., Hirsh-Pasek et al., 2015), this dissertation identifies whether evidence-based teaching strategies are used in the design of existing educational apps and experimentally tests how some tactics are more effective than others. Study 1 aims to understand how popular preschool literacy and math apps are designed and whether they connect with evidence-based teaching practices. This content analysis of 171 top literacy and math premium and free apps on Apple and Android app markets uses a defined spectrum of effective teaching tactics for young children identified in developmental and learning sciences (e.g., feedback, increasing complexity, guided play), to identify whether these tactics have been applied to current apps’ mechanics. Findings show there is a wide variety of features used across preschool apps, but few provide developmentally appropriate guidance for young learners, such as scaffolded feedback and leveling. Study 2 explores the direct effects of these features with 240 preschoolers, to experimentally test: a) which types of audible app feedback best support preschool learning, and b) whether preschoolers using an educational app with scaffolded challenge (i.e., leveling up) learn better than preschoolers using the same app with random ordered challenge. An ANCOVA and post-hoc Tukey test show that, of the participants who played the feedback tasks first (n=120), those with scaffolded feedback (i.e., explanations for correct and incorrect answers) were more accurate than participants with sound responses (i.e., bell, gong). However, this advantage disappeared when children played the leveling game first. Participants with encouraging (i.e., “Great job!” or “Try again!”) feedback took longer to complete tasks, compared to the sounds feedback group. Moreover, leveling results showed that gradually increasing challenge helped preschoolers make fewer incorrect responses and complete tasks faster than children playing the same game with random order leveling. Ultimately, improving the design of educational preschool apps through empirical research, like this, may be what our increasingly digital age needs to provide young children with high quality digital learning tools.