index.css

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  /* outline: 1px solid red; */
}

html {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

input {
  width: 100%;
  padding: 0.5em;
  border: 1px solid gray;
}

input[type="file"] {
  cursor: pointer;
}
input[type="file"]:hover {
  background-color: rgba(0, 0, 0, 0.05);
}
button {
  padding: 1em;
  border: 1px solid gray;
  cursor: pointer;
}
button:hover {
  background-color: rgba(0, 0, 0, 0.05);
}
button:active {
  background-color: rgba(0, 0, 0, 0.1);
}

label {
  display: grid;
  grid-auto-flow: row;
  padding: 0.5em;
  gap: 0.5em;
  background-color: rgba(0, 0, 0, 0.02);
  border: 1px solid gray;
}
label:hover {
  background-color: rgba(0, 0, 0, 0.05);
}

main {
  background-color: whitesmoke;
  color: #1e1e1e;
  display: grid;
  width: 100%;
  min-height: 100vh;
  grid-template-areas: 
    "controls preview"
    "results results";
  grid-template-columns: 1fr 1fr;
  grid-template-rows: 500px auto;
  padding: 1em;
  gap: 1em;
}

.panel {
  display: grid;
  grid-auto-flow: row;
  align-self: center;
  align-content: start;
  gap: 1em;
  grid-area: controls;
}

.panel .file-config {
  display: grid;
  grid-auto-flow: row;
  gap: 1em;
}

.panel .sheet-config {
  display: grid;
  grid-auto-flow: row;
  gap: 1em;
  grid-template-areas:
    "TITLE TITLE TITLE"
    "I1 I2 I3";
}

.panel .sheet-config h3 {
  grid-area: TITLE;
}

.panel .result-config {
  display: grid;
  grid-auto-flow: row;
  gap: 1em;
  grid-template-areas: 
    "TITLE TITLE"
    "I1 I2";
}

.panel .result-config h3 {
  grid-area: TITLE;
}

.preview {
  display: grid;
  grid-area: preview;
}

.preview canvas {
  background-color: rgba(0, 0, 0, 0.1);
}

.results {
  grid-area: results;
  /* display: grid; */
  /* grid-auto-flow: column; */
  /* gap: 1em; */
}

.results .partN {
  background-color: white;
  outline: 1px solid black;
}

.results .partN canvas {
  outline: 0.2em dashed rgba(0, 0, 0, 0.1);
}