Nice, but too easy. Up to 750 ish meters on day one and naturally up to surface on day 2 after I could spend nearly 200 diamonds on upgrades.
The booster doesn't need any fuel left and lets the player keep marching on to the next fuel, but doesn't help particularly good in steering/faster movement. So I had no reason not to hold on to them and use them as range extension.
Maybe add layers of denser material, slowing the gamer down, so we have to use the bossters more frequently or risk running dry on fuel...