Hard mode update

Now in this mode, the experience gain is slowed. No healing crystals from the boxes. The amount of enemies is increased, they are also stronger

Other changes

• Ice Spikes - the number of spikes has been reduced (15 in the base and +4 has been replaced by 5 in the base and +2)
• Black Hole - damage has been increased (100 in the base has been replaced by 200 in the base)
• Minor changes to mini bosses parameters (health and damage) - for more balance between them