Left drag: orbit. Right drag, middle drag or shift-drag: move. Wheel or the Zoom slider: zoom. Click a block: its id and position. Double-click a block: fly to it. Keys, with the view focused: arrows orbit, + and - zoom, 0 resets, P the panel, M the menu (top right: copy, save, full screen, walk, warnings, the clicked block), V walk.

Walk (V or the walker): click the view to look with the mouse (or drag, or the arrow keys). W A S D move, Space jumps, Space twice flies (then Space up, Shift down), W twice sprints, N goes through walls, V or Esc twice leaves. Doors, trapdoors and gates let you through.
Click a block: its id and position show here. Sliders and help: the panel button, top left, or P