Thanks for trying the game, and sorry for the confusion!
To start a round:
1. Click "LET'S DIG!" on the title screen (or press Enter).
2. The first time, a short practice board appears. Press SPACE (or click/tap) once to break the pillar, then enjoy the 7-second fever. You can also press SKIP.
3. The capybara then walks to the ice and waits. When you see "PRESS SMASH", press SPACE or click the red SMASH button. That starts the 77-second round.
In the round: move with WASD or the arrow keys. The hammer swings automatically, and SPACE is a stronger smash that also digs down. Hit the 7s, avoid the 1s.
The game pauses on purpose while it waits for your first SMASH, so it may have looked frozen. If it still stutters after the round starts, could you tell me your browser and device? I'd like to look into it.