Fix Plotly rendering: stronger line widths, white bg, Streamlit theme, NaN-safe arrays

app.py

@@ -259,7 +259,7 @@ def with_quota(alpha_d: float, beta_d: float, gamma_d: float,
 # ----------------------------
 
 def add_line(fig: go.Figure, q: np.ndarray, p: np.ndarray, name: str, color: str, dash: str = "solid") -> None:
-    fig.add_trace(go.Scatter(x=q, y=p, mode="lines", name=name, line=dict(color=color, dash=dash)))
+    fig.add_trace(go.Scatter(x=q, y=p, mode="lines", name=name, line=dict(color=color, dash=dash, width=2)))
 
 
 def add_filled_area(
@@ -405,8 +405,8 @@ def main() -> None:
     q_max = max(1.0, *[float(q) for q in q_candidates if np.isfinite(q)]) * 1.2
 
     q = np.linspace(0.0, q_max, 400)
-    p_d = demand_price(q, alpha_d, beta_d, gamma_d)
-    p_s = supply_price(q, alpha_s, beta_s, gamma_s)
+    p_d = np.nan_to_num(demand_price(q, alpha_d, beta_d, gamma_d), nan=0.0, posinf=0.0, neginf=0.0)
+    p_s = np.nan_to_num(supply_price(q, alpha_s, beta_s, gamma_s), nan=0.0, posinf=0.0, neginf=0.0)
 
     fig = go.Figure()
     add_line(fig, q, p_d, name="Demand", color="#1f77b4")
@@ -490,7 +490,8 @@ def main() -> None:
         yaxis_title="Price (P)",
         legend=dict(orientation="h", yanchor="bottom", y=1.02, xanchor="left", x=0),
         margin=dict(l=20, r=20, t=20, b=20),
-        template="plotly_white",
+        paper_bgcolor="white",
+        plot_bgcolor="white",
         height=560,
     )
 
@@ -499,7 +500,7 @@ def main() -> None:
     p_max = max(10.0, *[float(p) for p in p_candidates if np.isfinite(p)]) * 1.05
     fig.update_yaxes(range=[0, p_max])
 
-    st.plotly_chart(fig, use_container_width=True)
+    st.plotly_chart(fig, use_container_width=True, theme="streamlit")
 
     # ----------------------------
     # Downloads