Although digital interactive technology offers innovative, scarcely explored types of instruction, conventional analog paper booklets remain the main instruction format for children’s construction play. We examined how a fan-built, digital interactive instructions prototype affected children’s construction play compared to an analog booklet. We studied two LEGO building tasks among 20 eight-nine year-old boys. Ten used the prototype on an iPad, 10 the booklet. Using a quasi-experimental research design built on cognitive load theory, we found notable differences in the two construction play processes. Participants with the analog booklet had a faster, more fluent process, while the digital prototype group was more often distracted and seeking help. We propose basic design recommendations for digital interactive instructions for children’s construction play, i.e., include a rotational feature, animations, pace control, few buttons, and realistic colors.