Here are some instructions and tips for those who might need it:
Move Left: [Left Arrow]
Move Right: [Right Arrow]
Quickly Move Left: [Left Arrow], [Left Arrow] in quick succession
Quickly Move Right: [Right Arrow], [Right Arrow] in quick succession
Jump: [SPACE] / [Up Arrow] / [Down Arrow]
If the boulder hits you, it's game over. Even though the boulder is spherical, moving to the gaps on the left or right side of the corridor will not help you in dodging the boulder.
The 'K' bar at the top-left is the combo bar. Each item (gem, golden tank, or 'K' square) will increase the bar by 10%. Any time that you miss picking up an item, the entire bar will empty. This means that you'll have to collect 10 items consecutively in order to completely fill the combo bar, which will knock the boulder back as far as it can go.
You can only jump over lava rivers. You cannot jump over any of the statues. If you get hit by a lava river or statue, the boulder will move a little bit closer to you. Getting hit does not empty your combo bar, however - so in some cases it may be beneficial to sacrifice a hit in order to reach an item, and continue your combo.
Sometimes there are gems that are completely obscured by the statues. It sucks, but there's little that you can do about it. The best advice is to pay close attention to the time intervals between approaching items, and maybe doing a dash-roll behind a statue if you would expect a gem to be onscreen, but can't see one.