shift + Enter : run cell, select below
Ctrl + Enter : run cell
Alt + Enter : run cell, insert below
Y : to code
M : to markdown (설명문)
Z : undo last cell deletion
D,D : delete selected cell
B : insert cell below
X : cut selected cell
C : copy selected cell
Shift-V : paste cell above
V : paste cell below
Shift-M : merge cell below