Adjusting margins and header letter spacing.

assets/sass/_variables.scss

@@ -21,10 +21,10 @@ $print-font-size:     12pt;
 // Use like this: var(--fs-m)
 $font-size-fixed: (
   xxxxl:      3rem,
-  xxxl:       2.445rem,
+  xxxl:       2.5rem,
   xxl:        2rem,
-  xl:         1.556rem,
-  l:          1.223rem,
+  xl:         1.5rem,
+  l:          1.25rem,
   m:          1rem,
   s:          0.889rem,
   xs:         0.778rem,

assets/sass/base/forms/_forms.scss

@@ -10,7 +10,7 @@ form {
 input,
 textarea,
 select {
-  @include margin-bottom(.75);
+  @include margin-block(0 1);
 }
 
 // Mark field as required if needed.

assets/sass/base/grouping/_grouping.scss

@@ -57,7 +57,7 @@ li {
 
 header {
   // Add vertical rhythm margins.
-  @include margin-block(0 .3);
+  @include margin-block(0 .33);
 }
 
 // Horizontal rule
@@ -71,7 +71,7 @@ hr {
 
 p {
   // Add vertical rhythm margins.
-  @include margin-block(0 .75);
+  @include margin-block(0 1);
 
   // Set max text line width in main for readability.
   .main & {
@@ -83,7 +83,7 @@ p {
 
 pre {
   // Add vertical rhythm margins.
-  @include margin-block(0 .75);
+  @include margin-block(0 1);
   font-family: var(--ff-monospace);
 }
 

assets/sass/base/headings/_headings.scss

@@ -15,7 +15,7 @@ h5,
 %h5,
 h6,
 %h6 {
-  @include margin-block(1 .3, 'em');
+  @include margin-block(1 .33, 'em');
   color: var(--color-headings);
   font-family: var(--ff-headings);
   font-weight: var(--fw-headings);
@@ -38,16 +38,19 @@ h1,
   // h1 only on top of page so different margins.
   @include margin-block(1 .5, 'rem');
   font-size: var(--fs-xxl);
+  letter-spacing: -.01em;
 }
 
 h2,
 %h2 {
   font-size: var(--fs-xl);
+  letter-spacing: -.01em;
 }
 
 h3,
 %h3 {
   font-size: var(--fs-l);
+  letter-spacing: -.01em;
 }
 
 h4,