Update 0.23: resources and crafting

So, here's the serious change to the global gameplay. You won't find spells in the worlds now, instead you can collect resources to craft them. I might add spells you can find later, but they'll be very rare, and most likely hidden in some secret places and locked with puzzles.

There's also a tutorial now. I'll expand it as I add new mechanics in the next updates.

Let me know what you think of the new gameplay.

Change log:

• Added resources which can be collected from the worlds and crafted into spells.

• Added tutorial world.

• Birds will now flock more and attack together when provoked.

• Fixed bug that sometimes caused generated worlds to be empty.

• Fixed bugs that produced wrong distances to portal and castle. Mana recharging and Use Portal spell will work better now.

• Starting a new game in the used slot will now properly erase all old files.