1. Make a global variable Totalstarscollected = 0.
2. When Level 1 ends, add a system Event to add TotalStars variable's number to Totalstarscollected.
3. When Level 2 starts, reset TotalStars variable.
4. When Level 2 ends, add a system Event to add TotalStars variable's number to Totalstarscollected.
5. When level 3 starts, reset TotalStars variable and so on.
6. After all the levels are cleared, Player will be able to see how many stars were collected in total, by observing the Totalstarscollected variable.