➡ :move the "empty" cell toward right.
⬅ :move the "empty" cell toward left.
⬆ :move the "empty" cell toward up.
⬇ :move the "empty" cell toward down.
f :click the "Reset" button.
s :click the "Start" button.
a :click the "Pause" button.
p :click the "Play" button.
r :click the "Restart" button.
h :click the "Hide" button.
space:click the "space" button.