feat(plotly): implement sn-curve-basic (#7520)

## Implementation: `sn-curve-basic` - python/plotly

Implements the **python/plotly** version of `sn-curve-basic`.

**File:** `plots/sn-curve-basic/implementations/python/plotly.py`

**Parent Issue:** #3826

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/anyplot/actions/runs/26168194705)*

---------

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

Author: github-actions[bot]

plots/sn-curve-basic/implementations/python/plotly.py

@@ -1,76 +1,96 @@
 """ anyplot.ai
 sn-curve-basic: S-N Curve (Wöhler Curve)
 Library: plotly 6.7.0 | Python 3.13.13
-Quality: 80/100 | Updated: 2026-05-20
+Quality: 89/100 | Updated: 2026-05-20
 """
 
+import os
+
 import numpy as np
 import plotly.graph_objects as go
 
 
-# Data: Simulated fatigue test results for steel
+# Theme
+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"
+GRID = "rgba(26,26,23,0.10)" if THEME == "light" else "rgba(240,239,232,0.10)"
+
+# Okabe-Ito palette
+BRAND = "#009E73"  # position 1 — Basquin fit line
+C2 = "#D55E00"  # position 2 — test data markers
+C3 = "#0072B2"  # position 3 — ultimate strength
+C4 = "#CC79A7"  # position 4 — yield strength
+C5 = "#E69F00"  # position 5 — endurance limit
+
+# Data: Steel fatigue test data (Basquin model)
 np.random.seed(42)
 
-# Generate realistic S-N curve data with scatter
-# Basquin equation: S = A * N^b (where b is negative)
-A = 1200  # Material constant (MPa)
+A = 1200  # Fatigue coefficient (MPa)
 b = -0.12  # Fatigue strength exponent
 
-# Generate stress levels and corresponding cycles with scatter
 stress_levels = np.array([600, 550, 500, 450, 400, 350, 320, 300, 280, 260, 250, 240])
 cycles_base = (stress_levels / A) ** (1 / b)
 
-# Add scatter (multiple specimens at each stress level)
 cycles = []
 stress = []
 for s, n_base in zip(stress_levels, cycles_base, strict=False):
-    n_samples = np.random.randint(2, 5)  # 2-4 specimens per stress level
-    scatter = 10 ** (np.random.normal(0, 0.15, n_samples))  # Log-normal scatter
+    n_samples = np.random.randint(2, 5)
+    scatter = 10 ** (np.random.normal(0, 0.15, n_samples))
     for factor in scatter:
         cycles.append(n_base * factor)
         stress.append(s)
 
 cycles = np.array(cycles)
 stress = np.array(stress)
 
-# Material properties for reference lines
+# Material properties
 ultimate_strength = 650  # MPa
 yield_strength = 450  # MPa
 endurance_limit = 230  # MPa
 
-# Fit line data (smooth curve)
-fit_cycles = np.logspace(2, 8, 100)
+# Basquin fit line
+fit_cycles = np.logspace(2, 7, 100)
 fit_stress = A * fit_cycles**b
 
-# Create figure
+# Plot
 fig = go.Figure()
 
-# Add S-N curve fit line
 fig.add_trace(
-    go.Scatter(x=fit_cycles, y=fit_stress, mode="lines", name="Basquin Fit", line={"color": "#306998", "width": 4})
+    go.Scatter(
+        x=fit_cycles,
+        y=fit_stress,
+        mode="lines",
+        name="Basquin Fit",
+        line={"color": BRAND, "width": 3},
+        hovertemplate="Cycles: %{x:.2e}<br>Stress: %{y:.0f} MPa<extra>Basquin Fit</extra>",
+    )
 )
 
-# Add fatigue test data points
 fig.add_trace(
     go.Scatter(
         x=cycles,
         y=stress,
         mode="markers",
         name="Test Data",
-        marker={"color": "#FFD43B", "size": 14, "line": {"color": "#306998", "width": 2}},
+        marker={"color": C2, "size": 12, "line": {"color": PAGE_BG, "width": 1.5}},
+        hovertemplate="Cycles: %{x:.2e}<br>Stress: %{y:.0f} MPa<extra>Test Data</extra>",
     )
 )
 
-# Add horizontal reference lines as traces for legend visibility
-x_range = [100, 1e8]
+x_range = [100, 1e7]
+
+fig.add_hrect(y0=200, y1=endurance_limit, opacity=0.05, fillcolor=BRAND, layer="below")
 
 fig.add_trace(
     go.Scatter(
         x=x_range,
         y=[ultimate_strength, ultimate_strength],
         mode="lines",
         name=f"Ultimate Strength ({ultimate_strength} MPa)",
-        line={"color": "#D62728", "width": 3, "dash": "dash"},
+        line={"color": C3, "width": 2, "dash": "dash"},
+        hovertemplate=f"Ultimate Strength: {ultimate_strength} MPa<extra></extra>",
     )
 )
 
@@ -80,7 +100,8 @@
         y=[yield_strength, yield_strength],
         mode="lines",
         name=f"Yield Strength ({yield_strength} MPa)",
-        line={"color": "#2CA02C", "width": 3, "dash": "dash"},
+        line={"color": C4, "width": 2, "dash": "dash"},
+        hovertemplate=f"Yield Strength: {yield_strength} MPa<extra></extra>",
     )
 )
 
@@ -90,53 +111,61 @@
         y=[endurance_limit, endurance_limit],
         mode="lines",
         name=f"Endurance Limit ({endurance_limit} MPa)",
-        line={"color": "#9467BD", "width": 3, "dash": "dash"},
+        line={"color": C5, "width": 2, "dash": "dash"},
+        hovertemplate=f"Endurance Limit: {endurance_limit} MPa<extra></extra>",
     )
 )
 
-# Update layout
+# Style
 fig.update_layout(
-    title={"text": "sn-curve-basic · plotly · pyplots.ai", "font": {"size": 32}, "x": 0.5, "xanchor": "center"},
+    autosize=False,
+    paper_bgcolor=PAGE_BG,
+    plot_bgcolor=PAGE_BG,
+    hovermode="closest",
+    title={
+        "text": "sn-curve-basic · python · plotly · anyplot.ai",
+        "font": {"size": 16, "color": INK},
+        "x": 0.5,
+        "xanchor": "center",
+    },
     xaxis={
-        "title": {"text": "Cycles to Failure (N)", "font": {"size": 24}},
-        "tickfont": {"size": 18},
+        "title": {"text": "Cycles to Failure (N)", "font": {"size": 12, "color": INK}},
+        "tickfont": {"size": 10, "color": INK_SOFT},
         "type": "log",
-        "showgrid": True,
-        "gridwidth": 1,
-        "gridcolor": "rgba(0,0,0,0.1)",
+        "showgrid": False,
         "showline": True,
-        "linewidth": 2,
-        "linecolor": "black",
-        "range": [2, 8],  # 10^2 to 10^8
+        "linewidth": 1,
+        "linecolor": INK_SOFT,
+        "mirror": False,
+        "range": [2, 7],
+        "zerolinecolor": GRID,
     },
     yaxis={
-        "title": {"text": "Stress Amplitude (MPa)", "font": {"size": 24}},
-        "tickfont": {"size": 18},
+        "title": {"text": "Stress Amplitude (MPa)", "font": {"size": 12, "color": INK}},
+        "tickfont": {"size": 10, "color": INK_SOFT},
         "type": "log",
         "showgrid": True,
         "gridwidth": 1,
-        "gridcolor": "rgba(0,0,0,0.1)",
+        "gridcolor": GRID,
         "showline": True,
-        "linewidth": 2,
-        "linecolor": "black",
-        "range": [2.3, 2.9],  # ~200 to ~800 MPa
+        "linewidth": 1,
+        "linecolor": INK_SOFT,
+        "mirror": False,
+        "range": [2.3, 2.9],
+        "zerolinecolor": GRID,
     },
     legend={
-        "font": {"size": 18},
+        "font": {"size": 10, "color": INK_SOFT},
         "x": 0.95,
         "y": 0.95,
         "xanchor": "right",
         "yanchor": "top",
-        "bgcolor": "rgba(255,255,255,0.8)",
-        "bordercolor": "black",
-        "borderwidth": 1,
+        "bgcolor": "rgba(0,0,0,0)",
+        "borderwidth": 0,
     },
-    template="plotly_white",
-    margin={"l": 100, "r": 150, "t": 100, "b": 100},
+    margin={"l": 80, "r": 40, "t": 80, "b": 60},
 )
 
-# Save as PNG (4800 x 2700 px)
-fig.write_image("plot.png", width=1600, height=900, scale=3)
-
-# Save as HTML for interactive viewing
-fig.write_html("plot.html")
+# Save
+fig.write_image(f"plot-{THEME}.png", width=800, height=450, scale=4)
+fig.write_html(f"plot-{THEME}.html", include_plotlyjs="cdn")