Feature on a day of the week
To encourage people to play every day of the week, it is effective to make it meaningful to play tomorrow instead of today.
A good example of this would be “day-of-week quests”.
On Mondays, there are “wind materials” and on Tuesdays, “fire materials”. Tuesday: “Materials for Fire” Wednesday: “Materials for Water” Thursday: “Materials for Ground” Friday: “In-game currency” Saturday: “Materials for Dark” Sunday: “Materials for Light”
In this way, quests are prepared for each day of the week, and the rewards for these quests are materials for training characters with specific attributes.
This will increase the likelihood that players will log in the next day if they want to train a character with the fire attribute but do not have the materials and today is Monday.