Most difficult levels in existence?

[pillowpc2001]

I must admit, playing through this levels back in 2002 must have been quite an experience. I could see levels like Exit Chip and Warehouse II being difficult without solutions, and I've always wondered, how long have invalid tiles existed in Chip's Challenge? Were editors made to allow them or was the game allowed to do this from the start?

I couldn't solve Warehouse II without a solution, but I'm pretty sure I did Exit Chip on my own (except for looking in the editor, of course... ).

CC wasn't really "intended" for invalid tiles (hence why they are invalid... ). I assume they were possible since ChipEdit was first released, at which point people started making levels that had them... So CC was technically "allowed" to have them from the beginning, but there were no custom levels around yet...