Not enough sleep or disruptions to the sleep-wake cycle (such as those that may occur with shift work or travelling to a different time zone) cause the physiological state known as fatigue. Staying awake for 24 hours leads to a reduced hand-to-eye coordination that is similar to having a blood alcohol content of 0.1.
There are 13 hearts in a standard 52 card deck. There are also 13 diamonds, 13 spades and 13 clubs.
There are four suits: hearts, diamonds, spades and clubs. Thus there are 13 hearts, 13 diamonds, 13 spades and 13 clubs. The diamonds and hearts are printed in red. The spades and clubs are printed in black. So there are 26 red cards and 26 black cards. Each rank has four cards in it (one for each of the four suits).