Workbook Step 5 plus

More or less new topics:

• king in the middle
• queen ending
• pin
• bishop against pawn
• zugzwang

Elaborating the already introduced material:

• mini plan
  Opening the position, piece to a better square
• pawn ending
  The rook's pawn, tempo play, defending
• wrong bishop
  Winning and drawing positions
• vulnerability
  Exploiting vulneribility
• defending
  Defending against threats, a passed pawn, king's attack