replaced solver with faster solution

src/fhn_solver.jl

@@ -36,6 +36,7 @@ function fhn!(du, u, p::FHNParams, t)
 end
 
 function step!(U, V, params_obs::Observable; dx=1)
+    """
     p = params_obs[]
 
     # Flatten initial condition (activation u, recovery v)
@@ -55,6 +56,20 @@ function step!(U, V, params_obs::Observable; dx=1)
     U .= u_new
     V .= v_new
 
+    return U
+    """
+
+    params = params_obs[]
+
+    Δu = reshape(Laplacian.laplacian(U, params.N, params.dx), params.N, params.N)
+    Δv = reshape(Laplacian.laplacian(V, params.N, params.dx), params.N, params.N)
+
+    fu = params.Du * Δu .+ U .- (U .^ 3) ./ 3 .- V
+    fv = params.Dv * Δv .+ params.ϵ .* (U .+ params.a .- params.b .* V)
+
+    U .+= 0.1 .* fu
+    V .+= 0.1 .* fv
+
     return U
 end