Unlockable lives

I have implemented in my project a system of extra unlockable lives, to offer the player the opportunity to improve their robot (even if minimally).

Such lives can be purchased from the shop (whose currency is the blue crystals that are collected in each level) or be obtained at the end of the level by collecting all three green crystals.

Because now lives can be unlocked, it seemed clear to me that the minimum number of lives (the lives owned since the start of the game) should drop to three.

Furthermore, the fact of having reduced the number of lives to three creates a greater challenge for the player, who will have to be more cautious in moving within the game levels.