feat(altair): implement crossword-basic (#7456)

## Implementation: `crossword-basic` - python/altair

Implements the **python/altair** version of `crossword-basic`.

**File:** `plots/crossword-basic/implementations/python/altair.py`

**Parent Issue:** #3805

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/anyplot/actions/runs/26136687136)*

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: Markus Neusinger <2921697+MarkusNeusinger@users.noreply.github.com>

Author: 3 people

plots/crossword-basic/implementations/python/altair.py

@@ -1,24 +1,36 @@
-""" pyplots.ai
+""" anyplot.ai
 crossword-basic: Crossword Puzzle Grid
-Library: altair 6.0.0 | Python 3.13.11
-Quality: 92/100 | Created: 2026-01-15
+Library: altair 6.1.0 | Python 3.13.13
+Quality: 90/100 | Updated: 2026-05-20
 """
 
+import os
+import sys
+
+
+# Prevent the script's own directory from shadowing the 'altair' package
+sys.path = [p for p in sys.path if not p.endswith("/python")]
+
 import altair as alt
 import numpy as np
 import pandas as pd
 
 
-# Data - 15x15 crossword grid with symmetric black cell pattern
+# Theme tokens
+THEME = os.getenv("ANYPLOT_THEME", "light")
+PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
+INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
+INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"
+
+# Crossword cell colors (theme-adaptive monochrome design)
+CELL_ENTRY = "#FFFFFF" if THEME == "light" else "#DEDAD3"
+CELL_BLOCK = "#1A1A17" if THEME == "light" else "#3E3E3A"
+
+# Data — 15x15 crossword grid with 180-degree rotational symmetry
 np.random.seed(42)
 grid_size = 15
-
-# Create symmetric black cell pattern (180-degree rotational symmetry)
-# Start with empty grid (0 = white/entry cell, 1 = black/blocked cell)
 grid = np.zeros((grid_size, grid_size), dtype=int)
 
-# Define black cell positions for upper-left quadrant + center row/col
-# These will be mirrored for symmetry
 black_positions = [
     (0, 4),
     (0, 10),
@@ -43,7 +55,6 @@
     (7, 12),
 ]
 
-# Apply black cells with 180-degree rotational symmetry
 for r, c in black_positions:
     grid[r, c] = 1
     grid[grid_size - 1 - r, grid_size - 1 - c] = 1
@@ -54,58 +65,52 @@
 
 for r in range(grid_size):
     for c in range(grid_size):
-        if grid[r, c] == 1:  # Skip black cells
+        if grid[r, c] == 1:
             continue
-
-        # Check if this starts an across word (left edge or black cell to left, white to right)
         starts_across = (c == 0 or grid[r, c - 1] == 1) and (c < grid_size - 1 and grid[r, c + 1] == 0)
-
-        # Check if this starts a down word (top edge or black cell above, white below)
         starts_down = (r == 0 or grid[r - 1, c] == 1) and (r < grid_size - 1 and grid[r + 1, c] == 0)
-
         if starts_across or starts_down:
             numbers[(r, c)] = clue_num
             clue_num += 1
 
-# Build dataframe for grid cells
-cells_data = []
-for r in range(grid_size):
-    for c in range(grid_size):
-        cells_data.append(
-            {"row": r, "col": c, "is_black": grid[r, c] == 1, "color": "#1a1a1a" if grid[r, c] == 1 else "#ffffff"}
-        )
-
+# Build dataframes
+cells_data = [
+    {"row": r, "col": c, "color": CELL_BLOCK if grid[r, c] == 1 else CELL_ENTRY}
+    for r in range(grid_size)
+    for c in range(grid_size)
+]
 cells_df = pd.DataFrame(cells_data)
 
-# Build dataframe for clue numbers
-numbers_data = []
-for (r, c), num in numbers.items():
-    numbers_data.append({"row": r, "col": c, "number": str(num)})
-
-numbers_df = pd.DataFrame(numbers_data)
+numbers_df = pd.DataFrame([{"row": r, "col": c, "number": str(num)} for (r, c), num in numbers.items()])
 
-# Create grid cells chart
+# Grid cells layer
 cells = (
     alt.Chart(cells_df)
-    .mark_rect(stroke="#333333", strokeWidth=2)
+    .mark_rect(stroke=INK_SOFT, strokeWidth=1.5)
     .encode(x=alt.X("col:O", axis=None), y=alt.Y("row:O", axis=None), color=alt.Color("color:N", scale=None))
-    .properties(width=900, height=900)
 )
 
-# Create clue numbers overlay
+# Clue numbers overlay
 clue_numbers = (
     alt.Chart(numbers_df)
-    .mark_text(align="left", baseline="top", dx=-12, dy=-12, fontSize=14, fontWeight="bold", color="#333333")
+    .mark_text(align="left", baseline="top", dx=-12, dy=-12, fontSize=10, fontWeight="bold", color=INK_SOFT)
     .encode(x=alt.X("col:O", axis=None), y=alt.Y("row:O", axis=None), text="number:N")
 )
 
-# Combine layers and add title
+# Compose chart — square 600×600 canvas → 2400×2400 px at scale=4
 chart = (
     (cells + clue_numbers)
-    .properties(title=alt.Title("crossword-basic · altair · pyplots.ai", fontSize=32, anchor="middle", offset=20))
-    .configure_view(strokeWidth=0)
+    .properties(
+        width=600,
+        height=600,
+        background=PAGE_BG,
+        title=alt.Title(
+            "crossword-basic · python · altair · anyplot.ai", fontSize=16, anchor="middle", offset=18, color=INK
+        ),
+    )
+    .configure_view(fill=PAGE_BG, strokeWidth=0)
 )
 
 # Save outputs
-chart.save("plot.png", scale_factor=4.0)
-chart.save("plot.html")
+chart.save(f"plot-{THEME}.png", scale_factor=4.0)
+chart.save(f"plot-{THEME}.html")