Overall there are five game modes in Survivalcraft. Here is the list and a brief explanation. For more details, tap the mode name.
Creative is the easiest game mode to play in. In this mode the player is immortal and can fly, he/she also owns an infinite supply of all blocks and items. Creative is the only game mode in which animals can be spawned and the time of day changed at will. Hostile animals will not attack unless provoked.
Harmless game mode is the easiest of survival modes. Hostile animals will not attack unless provoked, and the player suffers less health damage then challenging game mode when harmed.
Challenging is the original game mode for survivalcraft. Hostile animals will attack no matter what, and it is pretty easy to die.
Cruel mode is made to mimic real life. It is the same as challenging, but with one catch; if you die, you will lose the world completely. cruel or what?
Probably the least used game mode, adventure makes it impossble to break any blocks without a tool of some sorts. It is most commonly used to make adventure maps.