diff --git a/monobiome/cli/scheme.py b/monobiome/cli/scheme.py
index 4080eb9..7e3e652 100644
--- a/monobiome/cli/scheme.py
+++ b/monobiome/cli/scheme.py
@@ -54,6 +54,7 @@ def register_parser(subparsers: _SubparserType) -> None:
     # particularly good measure of perceptual distinction, so we'd prefer the
     # former.
     parser.add_argument(
+        "-l",
         "--l-base",
         type=int,
         default=20,
@@ -82,7 +83,7 @@ def register_parser(subparsers: _SubparserType) -> None:
     parser.add_argument(
         "--term-fg-gap",
         type=int,
-        default=60,
+        default=65,
         help="Terminal foreground lightness gap (default: 60)",
     )
 
diff --git a/monobiome/constants.py b/monobiome/constants.py
index 317b897..3742771 100644
--- a/monobiome/constants.py
+++ b/monobiome/constants.py
@@ -16,6 +16,8 @@ L_max: int = parameters.get("L_max", 98)
 L_step: int = parameters.get("L_step", 5)
 
 L_points: list[int] = list(range(L_min, L_max+1))
+
+# L-space just affects accuracy of chroma max
 L_space = np.arange(0, 100 + L_step, L_step)
 
 monotone_C_map = parameters.get("monotone_C_map", {})
diff --git a/monobiome/scheme.py b/monobiome/scheme.py
index 1a94174..068ba93 100644
--- a/monobiome/scheme.py
+++ b/monobiome/scheme.py
@@ -98,7 +98,7 @@ def generate_scheme_groups(
 
     metric_map = {
         "wcag": lambda mc,ac: ac.contrast(mc, method='wcag21'),
-        "oklch": lambda mc,ac: mc.distance(ac, space="oklch"),
+        "oklch": oklch_distance,
         "lightness": lambda mc,ac: abs(mc.coords()[0]-ac.coords()[0])*100,
     }
     
@@ -131,6 +131,9 @@ def generate_scheme_groups(
         ("distance", distance),
         ("l_base", l_base),
         ("l_step", l_step),
+        ("fg_gap", fg_gap),
+        ("grey_gap", grey_gap),
+        ("term_fg_gap", term_fg_gap),
     ]
 
     # note how selection_bg steps up by `l_step`, selection_fg steps down by
@@ -157,7 +160,7 @@ def generate_scheme_groups(
     accent_pairs = [
         ("black", f"f{{{{{biome}.l{l_base}}}}}"),
         ("grey", f"f{{{{{biome}.l{l_base+grey_gap}}}}}"),
-        ("white", f"f{{{{{biome}.l{l_base+term_fg_gap-l_step}}}}}"),
+        ("white", f"f{{{{{biome}.l{l_base+term_fg_gap-2*l_step}}}}}"),
     ]
     for color_name, mb_accent in accent_color_map.items():
         aL = int(100*accent_colors[mb_accent].coords()[0])
@@ -184,29 +187,42 @@ def generate_scheme(
     term_color_map: dict[str, str],
     vim_color_map: dict[str, str],
 ) -> str:
+    l_sys = l_base
+    l_app = l_base + l_step
+
+    term_bright_offset = 10
+
+    # negate gaps if mode is light
+    if mode == "light":
+        l_step *= -1
+        fg_gap *= -1
+        grey_gap *= -1
+        term_fg_gap *= -1
+        term_bright_offset *= -1
+
     meta, _, mt, ac = generate_scheme_groups(
         mode, biome, metric, distance,
-        l_base, l_step,
+        l_sys, l_step,
         fg_gap, grey_gap, term_fg_gap,
         full_color_map
     )
 
     _, term, _, term_norm_ac = generate_scheme_groups(
         mode, biome, metric, distance,
-        l_base + l_step, l_step,
+        l_app, l_step,
         fg_gap, grey_gap, term_fg_gap,
         term_color_map
     )
     _, _, _, term_bright_ac = generate_scheme_groups(
         mode, biome, metric, distance,
-        l_base + l_step + 10, l_step,
+        l_app + term_bright_offset, l_step,
         fg_gap, grey_gap, term_fg_gap,
         term_color_map
     )
 
     _, _, vim_mt, vim_ac = generate_scheme_groups(
         mode, biome, metric, distance,
-        l_base + l_step, l_step,
+        l_app, l_step,
         fg_gap, grey_gap, term_fg_gap,
         vim_color_map
     )
diff --git a/monobiome/util.py b/monobiome/util.py
index 8fc70c1..9128649 100644
--- a/monobiome/util.py
+++ b/monobiome/util.py
@@ -1,3 +1,4 @@
+import math
 from types import GenericAlias
 from argparse import ArgumentParser, _SubParsersAction
 
@@ -6,5 +7,29 @@ from coloraide import Color
 _SubParsersAction.__class_getitem__ = classmethod(GenericAlias)
 _SubparserType = _SubParsersAction[ArgumentParser]
 
-def oklch_distance(mc: Color, ac: Color) -> float:
-    return mc.distance(ac, space="oklch")
+def oklch_distance(xc: Color, yc: Color) -> float:
+    """
+    Compute the distance between two colors in OKLCH space.
+
+    Note: `xc` and `yc` are presumed to be OKLCH colors already, such that
+    `.coords()` yields an `(l, c, h)` triple directly rather than first
+    requiring conversion. When we can make this assumption, we save roughly an
+    order of magnitude in runtime.
+
+    1. `xc.distance(yc, space="oklch")`: 500k evals takes ~2s
+    2. This method: 500k evals takes ~0.2s
+    """
+
+    l1, c1, h1 = xc.coords()
+    l2, c2, h2 = yc.coords()
+
+    rad1 = h1 / 180 * math.pi
+    rad2 = h2 / 180 * math.pi
+    x1, y1 = c1 * math.cos(rad1), c1 * math.sin(rad1)
+    x2, y2 = c2 * math.cos(rad2), c2 * math.sin(rad2)
+    
+    dx = x1 - x2
+    dy = y1 - y2
+    dz = l1 - l2
+    
+    return (dx**2 + dy**2 + dz**2)**0.5