Runes are special ability spells that can be slotted in sockets on your equipment. There are two types; active and passive. Passive runes are always activated when socketed. Active runes must be charged before they can be used. Each rune has a color that matches with a magic element. Matching the corresponding element will charge the meter at the bottom. The rune can be activated when the meter is full. You can switch between active runes by tapping the button at the bottom left. However, only the currently selected rune can be charged. After fully charging a rune, you can save it for later use by switching to another rune that is not ready. You can switch runes whenever the level is visible; including during cascade chains. The heal rune provided the tutorial can restore 250 points of health when activated. Because rune charges are kept between levels unless you are defeated, keep it around. The heal rune can prevent a failed level; keep it charged saved for emergencies. If you are sure you can recharge it quickly, use it to fill your health at the end of a level in order to be ready for the next level. Charge your heal ability with water tiles.