The game's main objective is to get gems and then reach the exit, while any number of lethal obstacles get in your way, such as falling rocks, dragons, explosions, fire and water, and floating skulls. The obstacles include the gems themselves, as a gem falling on your head will kill you. Depending on the level, you need to use careful planning, quick reflexes, or both. The game incorporates many elements from Boulder Dash, Chip's Challenge, Sokoban, and Laser Light.
There is also a second difficulty level, which requires you to get more gems in a level, reach a special and usually harder-to-reach exit, and imposes a time limit. In a nice twist, all tutorial levels have a secret room with a pretty difficult puzzle, which is required to solve the tutorial on hard mode. The original game contains 108 levels in the Prime level set; a level editor and yearly level design contest ensure that there are many more out there.
Sub Terra Draconis is the sequel.
This game provides examples of:
- Block Puzzle: Some levels borrow from Sokoban, and various obstacles can be defeated through pushing in the right block. Ice melts fire, cushions float on water, and so forth.
- Collision Damage: Touching an enemy kills you. Being adjacent to an enemy will kill you, unless you have the shield powerup.
- Control Room Puzzle: Several switches affect distant parts of the level; in some of them you are locked in a control room and have to solve the puzzle indirectly.
- Excuse Plot: The "plot" intentionally has absolutely nothing to do with the game.
- Expansion Pack: Once a year, featuring levels from the level design contests.
- Extreme Omnivore: The dragons, who will cheerfully eat rocks to get them out of your way. Of course, they will also eat you, given the chance.
- Fake Difficulty: In the fourth secret level, yes, the random shifting walls look really awesome and it's a clever gimmick... but due to the random nature of said level, there's no reliable way to beat it on hard mode before the time runs out. Really just a Luck-Based Mission, but the odds of the time running out before you finish the level are heavily against you.
- Light and Mirrors Puzzle: An explosion that catches a certain gem (the ruby) can create a laser which turns left when it hits a diamond, and right when it hits an emerald.
- Moon Logic Puzzle: From the PRIME set, "Euler" if you're playing on hard. The solution it requires is actually very simple and it's logical... but it's not natural for the game and there are NO hints for it - you have to figure out the "trick" yourself. Thankfully, it at least makes sense afterward, avoiding Guide Dang It!.
- No Fair Cheating - Various cheat codes exist, but completing a level with them simply doesn't count. The exception is the level warp cheat.
- Selective Gravity: Rocks and gems fall, most other things don't. This is common to the Digging Game genre.
- Spiritual Successor: To Supaplex; it even got the greenlight from the authors of Supaplex, and includes several of the levels from that game.
- Timed Mission - Every single level if you play on hard. If you play on easy, the time limit is just for bonus points.