I should quickly mention that there is only one level because I ran out of time. At the moment the hub world (the one with floating blobs of mercury) only has one level to go to, and the portal at the end of that level just takes you back to the hub world.
Next steps will be to make a UI that shows the player's number of lives, health, number of crystals collected, and number of Z's collected, add sound, and build more diverse levels. At the moment there is no significance to collecting anything, but eventually there will be. Think of the crystals like the gems from Spyro, and the Z's like the purple crystal in from crash bandicoot. Z's unlock levels, and collecting all the gems may unlock an alternate ending.