You Know You've Been Doing Too Much Hammer When...
... when you look to your kitchen, see a nice tile pattern that's 8x4 tiles and think
"Yea! They used a 256x128 units white_wall_tile003f brush".
"Yea! They used a 256x128 units white_wall_tile003f brush".
Yeah! 
useful tools and stuff here on TWP 
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When you are looking for your friend Bob and ask somebody if he has seen npc_bob.
When your in a parking lot early in the morning on a clear day and look at all the shadows cast by the cars and the light-posts and wonder what brightness the env_projectedtexture is set to.
lol... I did that this morning!
When you see that real world shadows get more diffracted the further they are from the object casting them and wish Source did the same thing.
[spoiler][SP] Alternate[/spoiler]
When you see that real world shadows get more diffracted the further they are from the object casting them and wish Source did the same thing.
Indeed. Pretty hard to do that in real-time, though (especially since the engine is busy doing a ton of other things as well).
When you align your silverware to the grid.
[spoiler][SP] Alternate[/spoiler]
...when you're at your local pizza place, look up that the ceiling and think: "Lol, noobs. They didn't align the ceiling textures properly!"
True story...
You're trying to make a large jump and wonder if it is 256 or another random number because the person who created the building is a n00b.