definetively not good that
you must having things clear if you try do something, and much times not simply "clear" also good balanced and calculated for it gives someclass of challenge to the players as Isr.goat said, keep it simple and with a objetive to reach
For example in my game Roguelike Heaven im doing (Is a 2D RPG game)
1) big maps conception pre-generation (cos its multiplayer then the idea of random-maps dont serve for this)
2) first of all a system combat of attack-strikesback with some class of weapons and basically with simple things as life bar, mana bar, thirsty bar, hungry bar and energy bar
3) some other objects in map like for example places where you find some FOOD/Drink in map and also a system for get QUESTS/MISSIONS (this dont have to be too much complex, can be simply find an object somewhere in map/game and deliver to a certain character)
4) a system for interconnect the maps (i use a kind of DOORS/PORTALS placed in a certain zone of the map for jump from a map to another)
5) scenary complementary objets like TREES/Houses/traps hidden etc
Then later you can going over add more things and complexity with the modification of code
but one thing is obvious "Rome dont made in 1 day" and things is much better start in simple way and then retouching and fixing and adding new things to it cos with new versions updated and enhanced is how you going building a great game/app