Aqua Fortis from only 1 atom...
c,5,13;c,1,9;b,7,11;t,7,7;b,11,7;t,3,7;m,1,11,90,1,clor;m,3,9,90,1,wwwwcrolwwww;m,8,9,90,1,cl2uuoddrwww;m,5,11,180,1,crruodllwwww;m,7,13,180,1,cwwwwwrolwww;m,3,13,270,1,wwwwwwwwcrol;m,1,7,90,1,wwclorwwwwww;m,5,7,180,1,wwwwcrrollww;m,9,7,180,1,wwwwwcrrollw;m,12,5,90,3,cddouuwwwwww;m,11,3,180,2,luwcdd22ru2o;
Brimstone in 60 symbols
t,3,7;t,1,9;c,3,11;c,11,11;t,13,9;t,11,7;b,5,9;b,6,7;m,6,13,180,2,wwcruodlww;m,3,9,90,3,cddrrroruu;m,5,11,270,1,cuuoddwwww;m,9,7,90,1,crolwwwwww;m,7,5,90,1,crrollwwww;m,11,9,90,3,cddllloluu;
Haematite - this should probably jam at some time...
p,10,11;b,7,9;b,1,5;m,7,11,90,1,cluodrwww;m,10,9,90,1,wwwcrolww;m,13,11,90,1,crwowlwww;m,5,9,0,2,wwwwwcdou;m,2,9,0,3,c1lor;m,1,11,90,1,crrollwwwwwwwwwwww;m,1,7,90,1,crrollwwwwwwww;m,3,7,270,1,crol;m,8,7,180,2,cr22uodl;
3 from 1:
c,5,13;c,1,9;b,7,11;t,7,7;b,11,7;t,3,7;m,1,11,90,1,clor;m,3,9,90,1,wwwwcrolwwww;m,8,9,90,1,cl2uuoddrwww;m,5,11,180,1,crruodllwwww;m,7,13,180,1,cwwwwwrolwww;m,3,13,270,1,wwwwwwwwcrol;m,1,7,90,1,wwclorwwwwww;m,5,7,180,1,wwwwcrrollww;m,9,7,180,1,wwwwwcrrollw;m,12,5,90,3,cddouuwwwwww;m,11,3,180,2,luwcdd22ru2o;
Where is the logical sequence of thinking in solving the red and yelow blocks? That involves far too many leaps for my liking. Lots of work in making this though.
The mapping of next spell / previous spell might be easier if it was q = lightnig, W = fire, E = necro hand, i.e. direct correlation. Otherwise you have to keep looking to see what you have to work out whether to go 1 up or 1 down. Otherwise, quite clever in concept. I also agree about the enemies being able to attack from within the ground being a bit annoying.
The ability to aim all the way to the sides changes and the gun doesn't follow the mouse very well. Also the 'upgrades' don't seem much better, except rate of fire.