Instructions:

Keyboard:

Press r, or c to hold current piece.
Press the a key to move left, d to move right, and w to rotate
Pressing the s key will move the currently active piece down by one
Pressing the space bar will hard drop the currently active piece

Touch (mobile):

Swipe up to hold current piece.
Drag left on field to move left, drage right to move right, and tap to rotate
Dragging downwards will drag the piece down
Swiping down will hard drop the currently active piece