Performance: Use PNGs for the background gradients

It turns out that for a blurry gradient background, low-res raster images look very convincing when scaled up and interpolated. That means that we can rasterize our gradient SVGs for improved paint performance when resizing the window, while still keeping them quite lightweight (just a couple of kilobytes each).

src/graphics/desktop-gradient.svg

@@ -1,16 +0,0 @@
-<svg width="1440" height="800" viewBox="0 0 1440 800" fill="none" xmlns="http://www.w3.org/2000/svg">
-<g filter="url(#filter0_f_4162_80259)">
-<path d="M-37.0486 666.028C267.76 138.867 944.304 -46.1945 1477.05 260.929" stroke="url(#paint0_linear_4162_80259)" stroke-width="192" stroke-linecap="round"/>
-</g>
-<defs>
-<filter id="filter0_f_4162_80259" x="-333.118" y="-183.694" width="2106.24" height="1145.68" filterUnits="userSpaceOnUse" color-interpolation-filters="sRGB">
-<feFlood flood-opacity="0" result="BackgroundImageFix"/>
-<feBlend mode="normal" in="SourceGraphic" in2="BackgroundImageFix" result="shape"/>
-<feGaussianBlur stdDeviation="100" result="effect1_foregroundBlur_4162_80259"/>
-</filter>
-<linearGradient id="paint0_linear_4162_80259" x1="1255.31" y1="320.254" x2="184.899" y2="607.497" gradientUnits="userSpaceOnUse">
-<stop stop-color="#00C59E"/>
-<stop offset="0.75" stop-color="#0044A5"/>
-</linearGradient>
-</defs>
-</svg>

src/graphics/mobile-gradient.svg

@@ -1,86 +0,0 @@
-<?xml version="1.0" encoding="UTF-8" standalone="no"?>
-<svg
-   width="1200"
-   height="285"
-   viewBox="0 0 1200 285"
-   fill="none"
-   version="1.1"
-   id="svg5"
-   xmlns="http://www.w3.org/2000/svg"
-   xmlns:svg="http://www.w3.org/2000/svg">
-  <g
-     filter="url(#filter0_f_3970_9366)"
-     id="g2"
-     transform="translate(422.00201)">
-    <path
-       d="m -164.342,495.134 c 188.2881,-188.288 494.684,-190 684.684,0"
-       stroke="url(#paint0_linear_3970_9366)"
-       stroke-width="235.517"
-       stroke-linecap="round"
-       id="path1"
-       style="stroke:url(#paint0_linear_3970_9366)" />
-    <path
-       d="m -164.342,495.134 c 188.2881,-188.288 494.684,-190 684.684,0"
-       stroke="url(#paint1_linear_3970_9366)"
-       style="mix-blend-mode:overlay;stroke:url(#paint1_linear_3970_9366)"
-       stroke-width="235.517"
-       stroke-linecap="round"
-       id="path2" />
-  </g>
-  <defs
-     id="defs5">
-    <filter
-       id="filter0_f_3970_9366"
-       x="-517.617"
-       y="-0.00012207"
-       width="1391.23"
-       height="848.409"
-       filterUnits="userSpaceOnUse"
-       color-interpolation-filters="sRGB">
-      <feFlood
-         flood-opacity="0"
-         result="BackgroundImageFix"
-         id="feFlood2" />
-      <feBlend
-         mode="normal"
-         in="SourceGraphic"
-         in2="BackgroundImageFix"
-         result="shape"
-         id="feBlend2" />
-      <feGaussianBlur
-         stdDeviation="117.758"
-         result="effect1_foregroundBlur_3970_9366"
-         id="feGaussianBlur2" />
-    </filter>
-    <linearGradient
-       id="paint0_linear_3970_9366"
-       x1="349.17099"
-       y1="323.96301"
-       x2="6.82898"
-       y2="666.30499"
-       gradientUnits="userSpaceOnUse">
-      <stop
-         stop-color="#0D5CBD"
-         id="stop2" />
-      <stop
-         offset="0.730863"
-         stop-color="#0DBDA8"
-         id="stop3" />
-    </linearGradient>
-    <linearGradient
-       id="paint1_linear_3970_9366"
-       x1="349.17099"
-       y1="323.96301"
-       x2="6.82898"
-       y2="666.30499"
-       gradientUnits="userSpaceOnUse">
-      <stop
-         stop-color="#0D5CBD"
-         id="stop4" />
-      <stop
-         offset="0.730863"
-         stop-color="#0DBDA8"
-         id="stop5" />
-    </linearGradient>
-  </defs>
-</svg>

src/index.css

@@ -74,20 +74,23 @@ body {
   -webkit-tap-highlight-color: transparent;
 }
 
-@media (min-height: 330px) {
+@media (min-height: 33px) {
   body[data-background="gradient"]::before {
     content: "";
     position: fixed;
-    inset: 0;
-    background-image: url("graphics/mobile-gradient.svg");
-    background-size: auto;
+    /* Chromium abruptly fades our images to fully transparent at the edge of
+    the element. If we just make the element a little bigger than the viewport,
+    this is no longer visible. */
+    inset: -20px;
+    background-image: url("graphics/mobile-gradient.png");
+    background-size: 1400px 305px;
     background-position: bottom;
     background-repeat: no-repeat;
   }
 
   body[data-background="gradient"][data-platform="desktop"]::before {
-    background-image: url("graphics/desktop-gradient.svg");
-    background-size: calc(max(1440px, 100vw)) calc(max(800px, 100vh));
+    background-image: url("graphics/desktop-gradient.png");
+    background-size: max(1440px, 100vw) max(1440px, 100vh);
     background-position: center;
   }
 }