Every track lays out its steps as a horizontal row of square cells. Click a cell to toggle. Click-drag horizontally across cells to paint them all on (or all off, depending on what the first cell was). Many gestures are stacked on the cell:

Cell gestures

• Click — toggle on/off.
• Drag horizontally across multiple cells — paint mode. The drag origin's initial state determines whether the stroke turns cells on or off.
• Shift + drag vertically — adjust velocity (1–127). The cell shows the level as a filled bar from the bottom.
• Drag vertically (on synth tracks) — adjust the step's pitch (note override). Each pixel ≈ one semitone.
• ⌃/⌘ + click — open the Step Inspector in the bottom panel.
• Alt + click on a synth track — toggle Accent on the step.
• Shift + alt + click on a synth track — toggle Slide(303-style legato glide from the previous note).

Visual indicators on a cell

Active step, solid color, fill height = velocity.
A green tick on the LEFT = the step was tapped slightly ahead of the grid.
A red tick on the RIGHT = the step was tapped slightly behind the grid.
The orange A = accent enabled. The cyan S = slide enabled (synth tracks only).

The playhead

A glowing cyan bar travels across each track's row in sync with the audio. It's calculated from AudioContext.currentTime, so it leads the audio by exactly zero — what you see is what you hear.