shirt + direction key: everytime move 10 pixels
crtl + 0: use current screen for the image
crtl + t: adjust image
crtl + g: merge selected layer into a group
crtl + r: show or hide ruler
crtl + d: cancel the selection
crtl + f: duplicate filter
crtl + alt + f: pop up duplicate filter
alt + backspace: paint using front color
alt + delete: paint using background color
shift is import for ruler