diff --git a/src/plot.rs b/src/plot.rs
index 3207e74..4f11b2d 100644
--- a/src/plot.rs
+++ b/src/plot.rs
@@ -51,6 +51,8 @@ impl Ring {
     }
 }
 
+/// Plain rounding map (used by tests; hysteresis variant is used in render).
+#[allow(dead_code)]
 fn levels(samples: &[f64], max: f64, rows: usize) -> Vec<usize> {
     // Row 0 = top of the plot = max value.
     samples
@@ -152,16 +154,33 @@ pub fn render(
     };
 
     let st = Style::default().fg(color);
+    // nvtop's connected staircase (plot.c lines 55-107, pattern only):
+    // on a step, the corner glyphs *join* the horizontals — old level gets
+    // a corner open toward the incoming line, new level a corner open
+    // toward the outgoing line, '│' strictly between. Every horizontal run
+    // therefore connects to the next through a corner, no gaps.
     for (c, &l) in lvls.iter().enumerate() {
-        set(l, c, '─', st);
-        if c > 0 {
-            // Vertical join strictly BETWEEN the levels (endpoints excluded:
-            // both endpoint rows already carry '─' — overwriting them with
-            // '│' erased the level dash on every transition column, the
-            // "─│─│" comb). Subagent-diagnosed off-by-one.
-            let prev = lvls[c - 1];
-            let (top, bot) = if prev < l { (prev, l) } else { (l, prev) };
-            for r in top + 1..bot {
+        if c == 0 {
+            set(l, c, '─', st);
+            continue;
+        }
+        let prev = lvls[c - 1];
+        if prev == l {
+            set(l, c, '─', st);
+        } else if prev < l {
+            // value fell: line steps DOWN screen. Old level: '╮' (opens
+            // left toward incoming). New level: '╰' (opens right toward
+            // outgoing). '│' between.
+            set(prev, c, '╮', st);
+            set(l, c, '╰', st);
+            for r in prev + 1..l {
+                set(r, c, '│', st);
+            }
+        } else {
+            // value rose: line steps UP screen. Old level: '╯', new: '╭'.
+            set(prev, c, '╯', st);
+            set(l, c, '╭', st);
+            for r in l + 1..prev {
                 set(r, c, '│', st);
             }
         }