body { font-family: system-ui, sans-serif; margin: 0; background: #f6f7f9; }
header { background: #1a202c; color: white; padding: 12px 20px; display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; }
main { display: grid; grid-template-columns: 220px 1fr; gap: 16px; padding: 16px; }
aside, #inbox, #reader, #composer { background: white; border-radius: 8px; padding: 12px; box-shadow: 0 1px 3px rgba(0,0,0,.1); }
#inbox { grid-column: 2; }
.email-item { border-bottom: 1px solid #eee; padding: 8px; cursor: pointer; }
.email-item:hover { background: #f0f4ff; }
label { display: block; margin: 8px 0; }
input, select, textarea { width: 100%; padding: 8px; margin-top: 4px; }
button { margin: 4px 4px 4px 0; padding: 8px 12px; cursor: pointer; }
.hidden { display: none; }
#r-body { border-top: 1px solid #ddd; margin-top: 8px; padding-top: 8px; white-space: pre-wrap; }
#settings-bar input { width: auto; }
.mailbox-btn { display: block; width: 100%; text-align: left; margin-bottom: 4px; }
.mailbox-btn.active { background: #2b6cb0; color: white; }