The Locked House of Dr. Matrix

A Puzzle Hunt by Wei-Hwa Huang
that occurred during G4G8, March 2008

THE RULES:

You can solve the puzzles in any order.  However, competitive players will
probably solve most, if not all, of the puzzles in the order suggested by
Dr. Matrix:  solve a puzzle,  distill the answer into a single letter,
then go to the next puzzle with that letter.

Each player should use a puzzle log to record puzzle IDs and answers.
The puzzle log has four columns: write the identification letter of the puzzle
in column 1, the solution of the puzzle in column 2, the single letter
that the solution encodes to in column 3, and the encrypted five-letter word
in the lower-left corner of each puzzle in column 4.  On the next line,
copy the "Next" letter to the first column, and then solve that puzzle.  Repeat.

The encoding adds the ranks of the letters in the word modulo 26.  Examples:
   A1 C3 T20 = X24
   A1 C3 T20 S19 = Q17
   A1 R18 T20 S19 = F6

Some puzzles have an upside down HINT at the bottom of the puzzle.
Don't be fooled; this is a hint for a different puzzle.
The starting text of each puzzle will tell you if a hint for that
puzzle is available and, if so, at what puzzle you will find it.

Once you have solved at least 13 puzzles, you may go onto Phase 2.