Yank/paste via one unnamed register: `y` operator (yy/yw/yiw/y$), `p`/`P`, with `x`/`d`/`c` also filling it so `dd`…`p` moves a line. Undo/redo (`u`, `Ctrl-r`) as bounded full-buffer snapshots — one Insert session is one undo group. `.` replays the last change from its recorded keystrokes, so it repeats insert sessions like `ciwfoo<Esc>`.