It's the trigger. Do you know I tried all 4 face buttons, found they were doubled up (2 jumps, 2 dashes) and without a spare thought, I intuitively took from that there are no more controls (otherwise why would they double up instead of adding more actions to those buttons?) And I definitely wouldn't have thought to pull triggers in a retro game.
Dev team; if you had no time for a tutorial or prompt in a week, I get it - but not even a control description on the Itch page like every other mini game on Itch?