There is a Saves folder in the archive - put it in the game folder (or another place - depends on the release).

So, in each chapter you need to find a hidden blue heart and a cassette (8 hearts, 8 cassettes).

The cassette opens up a more difficult mode for the chapter: B-Side, in which you need to find a red heart (+8 hearts).

After completing the game, the C-Side mode opens - even more difficult, in which you need to find 8 gold hearts (+ 8 hearts).

To open Chapter 8, you need at least 4 hearts.

To unlock the B-Side for Chapter 8, you need to collect 15 hearts in the previous chapters.

To open the C-Side for Chapter 8, you need to collect 23 hearts in the previous chapters.

After receiving the first 16 hearts, for each completed chapter, the golden strawberry mode opens - you need to pick it up at the beginning of the level and carry it to the end without dying once. In total, you can collect +24 bonus strawberries (8 chapters * 3 modes), as a result, the strawberry counter will show 199/175.