diff --git a/src/bin/flat.rs b/src/bin/flat.rs
index 597b29f..3b374e0 100644
--- a/src/bin/flat.rs
+++ b/src/bin/flat.rs
@@ -78,6 +78,7 @@ impl Metric for Coil {
 
 mod riemann {
 	use glm::*;
+	use glm::ext::pow2;
 	use num_traits::identities::Zero;
 
 	pub struct Decomp2 {
@@ -95,6 +96,11 @@ mod riemann {
 			transpose(&h.ortho) * diagonal(h.diag * h.diag) * h.ortho
 		}
 
+		fn invmetric(&self, pos: Vec2) -> Mat2 {
+			let h = self.halfmetric(pos);
+			transpose(&h.ortho) * diagonal(Vec2::from_s(1.0) / pow2(h.diag)) * h.ortho
+		}
+
 		fn dmetric(&self, pos: Vec2) -> Tens2 {
 			part_deriv(|p| self.metric(p), pos, 1.0e-3)
 		}
@@ -141,7 +147,7 @@ mod riemann {
 
 	fn krist(space: &impl Metric, pos: Vec2) -> Tens2 {
 		// Γ^i_k_l = .5 * g^i^m * (g_m_k,l + g_m_l,k - g_k_l,m)
-		let g = inverse(&space.metric(pos)); // с верхними индексами
+		let g = &space.invmetric(pos); // с верхними индексами
 		let d = space.dmetric(pos);
 		let mut ret: Tens2 = [Mat2::zero(); 2];
 		// ret[i][l][k] = sum((m) => .5f * g[m][i] * (d[k][l][m] + d[l][k][m] - d[m][k][l]))