Sleep is one of the most essential elements for our health. Nevertheless, overall sleep hygiene is going to decrease nowadays. One of the major reasons that worsens sleep hygiene is our smartphone use before sleep. Thus, this study aims to explore design opportunities for improving sleep hygiene by inducing people to reduce their smartphone use in an unobtrusive manner. To figure out habitual behaviors related with smartphone use before sleep, we have conducted a series of focus group interviews. The results indicated that participants tend to use their smartphone without being aware of the negative influence on sleep quality. Based on the findings, we developed apparatus with ambient lighting. We deployed and interviewed its uses through a field study with eight participants. To conclude, the ambient lighting notification could help them to be easily aware of their smartphone use patterns and reduce its usage time before sleep. The implications and further study are discussed as well.