The controls are given in a short text blurb at the start of each level. I think the first level is broken though at the moment so here is the blurb that should be showing.
"Cross the log without falling off. Be careful!! Hold left and right to maintain balance. Hold up to move forward. You can either move or balance, not both." Press A to start the level.
Sorry it definitely isn't ideal atm but it is technically playable