TUMBLE is a canvas game. The board takes the keyboard only while it has focus — click it or tab to it first. Title screen: Space starts hard-block mode, H starts soft-block mode where pieces deform permanently when they land. In play: A / D push the falling block sideways, Q / E apply spin, S accelerates the fall, Space slams the block down, P pauses, R restarts in the same mode, I toggles solver telemetry. 1 / 2 / 3 set difficulty at any time, which sets the band-clear threshold to 74, 82 or 88 percent. Score and state are announced in the on-canvas panels.