http://proveyourlogic.com/
Kind of fun.. A bit tough at times. Im on 11 as I type this
Level 1
level 2
level 3
level 4
level 5
level 6
level 7
level 8
level 9
level 10
level 11
level 12
level 13
Just got game over on lv 14... And its 1:30 am, so Im going to sleep...