i added details by selecting tiles that should have added details, storing the tile numbers as variables on a code page (the 2nd one), then programming on the next (3rd) codepage how the tiles should be decorated.
the last (4th) code page has only the main loop, and the first one has no code because it's for a bit of extra documentation.

the decogen…draw() (decoration generation draw) function checks every tile for if it's one of the special tiles, and then decorates if it is.
each tile has distinct decorations, so they have very different approaches to being decorated:

• pillars are generated from the base (the only pillar sprite in the spritesheet).
  they check for a ledge above to know how long the pillar should be.
  when they hit it, the rest of the pillar is drawn from top to bottom, with three parts
  • the base sprite but mirrored, is the capital (the top)
  • a dark line shades the capital
  • a rectangle connects the base and the capital
• every brick wall tile on the map checks if it is below a ledge tile.
  if it is, it draws a shaded row of bricks below the ledge
  using a one-off character that i made in my one-off character creator
• the lamp's decoration has two parts
  • the pole is almost like a pillar, but in reverse:
    the lamp checks the tiles below the bulb (the only lamp sprite) until it hits the floor,
    then it draws the pole. it has four parts
    • mirrored base sprite as capital
    • line that shades the capital
    • rectangle that connects the pillar
    • base sprite used as-is for the base
  • the emission lines are just six lines that get drawn next to the bulb — no checks needed
• the door has only its bottom tile in the spritesheet.
  the part above gets generated — no checks needed.
  it has 4 parts
  • the top third of the door is another one-off character
  • the row of bricks above is another one-off character, but only the bright pixels
  • the single dark pixel of the brick row is drawn with pset()
  • i added a black outline to the left and right of the door
    using 2 lines
• the clock is also getting decorated with no checks. the decoration has 3 parts
  • a black filled circle for the clock face
  • a bright hollow circle for the outline
  • because the filled circle overdrawed the clock hands,
    the clock hands sprite gets replaced
• every cloud tile checks if it has an empty background tile to its left or right.
  if it has, it draws a line to complete the outline

before	after