Points for each level=star bonus+time bonus+objects bonus+chances bonus
1 star=500
1 object left=500
no chance used=1500(pass on first go after entering a level from menu)
no time consumption=1000(it always takes some time so you are not able to get 1000)
total=500 x stars + 500 x objects left + 1500 + around(800-500)(estimated time consumption for hard levels)

To reach 500000 points in all 143 levels = 3496.5 points per level

For some reason, it's not possible to get above 3496 points in all 143 levels. So I highly recommend you to start from level 1. Try to "buy" as many points as you can in one level then move to the next. If you want to give it a pause or just want to skip it, you can take down the current level for replaying.

But how to get a "high" score?
1. Don't depend on hints
Well first you should basically get rid of hints. Because hints always use all the objects and consume unnecessary time for most levels. Your star bonus and chance bonus will be reduced as well. (For example, on level 1 you can only get around 1884 points with hints but around 3778 by playing manually)Unless for extremely hard levels, in that case, hints can be your only choice but you need to make sure to quit the current level and re-enter it for using hints. (immediately use a hint after entering the level for a higher score).

2. Make sure the chance bonus is 1500 on every level
You can firstly practice several times on one level then quit to the menu and reenter hoping for good luck to finish with least objects and most stars.

3. Objects left over stars earned
For some levels that provide many objects, ignore the stars that are hard to achieve. Directly trigger the handle/button/spider/crossbow/pot etc. Only when sometimes you can trade one object for two stars and not consume much time then it's worth doing so.

4. Compare your score to rank
After completing a level, a rank should pop up and display your best record. To my experience, if you can reach the top 50 in one level then it's a good score. You might notice that some players cheated for impossible high scores, just ignore them and refer to reasonable high scores. For me I even reached the top 3 in a level.

In case you might ask why there is no picture shown for reference to quick solve every level. Well that's the most annoying part of the game. It doesn't let you take a screenshot for solutions after finishing levels even if you performed perfectly.