:root {
  color-scheme: light;

  /* Palette */
  --base64-bg: #f3f6f9;
  --base64-panel: #ffffff;
  --base64-soft: #f6f8fb;
  --base64-border: #cbd5e1;
  --base64-border-strong: #94a3b8;
  --base64-text: #162033;
  --base64-muted: #5b677a;
  --base64-primary: #0969da;
  --base64-primary-hover: #0757b8;
  --base64-focus: #60a5fa;
  --base64-success: #18794e;
  --base64-success-bg: #ecfdf3;
  --base64-warning: #8a4b08;
  --base64-warning-bg: #fff7df;
  --base64-error: #b42318;
  --base64-error-bg: #fff1f0;
  --base64-on-primary: #ffffff;
  --base64-control-bg: #ffffff;
  --base64-control-subtle-bg: #f8fafc;
  --base64-control-hover-bg: #eef2f7;
  --base64-info: #075985;
  --base64-info-bg: #eaf7ff;
  --base64-info-border: #a9ddf7;
  --base64-drag-bg: #edf6ff;
  --base64-success-border: #a7d7bd;
  --base64-warning-border: #efd28e;
  --base64-error-border: #f0b4ae;

  /* Typography and dimensions */
  --base64-font-ui: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans JP", sans-serif;
  --base64-font-code: "Cascadia Code", Consolas, monospace;
  --base64-content-max-width: 1200px;
  --base64-page-gutter: 32px;
  --base64-page-gutter-mobile: 20px;
  --base64-layout-gap: 14px;
  --base64-control-min-height: 38px;
  --base64-input-min-height: 40px;
  --base64-editor-min-height: 310px;

  /* Shared component geometry */
  --base64-border-width: 1px;
  --base64-radius-panel: 12px;
  --base64-radius-section: 10px;
  --base64-radius-toolbar: 9px;
  --base64-radius-control: 8px;
  --base64-radius-compact: 7px;
}

/* Page frame */
.base64-page,
.base64-page * { box-sizing: border-box; }

.base64-page {
  margin: 0;
  background: var(--base64-bg);
  color: var(--base64-text);
  font-family: var(--base64-font-ui);
}

.base64-main {
  width: min(var(--base64-content-max-width), calc(100% - var(--base64-page-gutter)));
  margin: 0 auto;
  padding: 28px 0 52px;
}

.base64-page-header { margin-bottom: 18px; }
.base64-page-header h1 { margin: 10px 0 6px; font-size: clamp(1.65rem, 3vw, 2.2rem); }
.base64-page-header p { margin: 0; color: var(--base64-muted); }
.base64-breadcrumb { display: flex; gap: 8px; align-items: center; font-size: .88rem; }
.base64-breadcrumb a { color: var(--base64-primary); }

/* Shared panels */
.base64-notice,
.base64-panel {
  border: var(--base64-border-width) solid var(--base64-border);
  border-radius: var(--base64-radius-panel);
  background: var(--base64-panel);
}

.base64-notice {
  margin-bottom: 14px;
  padding: 12px 16px;
  color: var(--base64-info);
  background: var(--base64-info-bg);
  border-color: var(--base64-info-border);
}

.base64-panel { margin-bottom: 16px; padding: 18px; }
.base64-panel-heading { display: flex; justify-content: space-between; align-items: flex-start; gap: 18px; margin-bottom: 16px; }
.base64-panel-heading h2,
.base64-panel h3,
.base64-panel h4 { margin-top: 0; }
.base64-panel-heading h2 { margin-bottom: 4px; font-size: 1.15rem; }
.base64-panel-heading p { margin: 0; color: var(--base64-muted); font-size: .92rem; }

/* Text converter controls */
.base64-mode-tabs {
  display: inline-grid;
  grid-template-columns: repeat(2, minmax(90px, 1fr));
  padding: 3px;
  border: var(--base64-border-width) solid var(--base64-border);
  border-radius: var(--base64-radius-toolbar);
  background: var(--base64-soft);
}

.base64-mode-tab {
  min-height: var(--base64-control-min-height);
  padding: 7px 16px;
  border: 0;
  border-radius: 6px;
  background: transparent;
  color: var(--base64-text);
  font: inherit;
  font-weight: 700;
  cursor: pointer;
}
.base64-mode-tab.is-active {
  background: var(--base64-primary);
  color: var(--base64-on-primary);
}

.base64-toolbar,
.base64-action-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px var(--base64-layout-gap);
}
.base64-toolbar { margin-bottom: 14px; padding: 12px; border-radius: var(--base64-radius-toolbar); background: var(--base64-soft); }
.base64-fieldset { display: flex; flex-wrap: wrap; align-items: center; gap: 9px 15px; margin: 0; padding: 0; border: 0; }
.base64-fieldset legend { float: left; margin-right: 12px; font-weight: 700; }
.base64-fieldset label,
.base64-check { display: inline-flex; align-items: center; gap: 6px; cursor: pointer; }
.base64-fieldset input,
.base64-check input { width: 17px; height: 17px; accent-color: var(--base64-primary); }
.base64-shortcut { margin-left: auto; color: var(--base64-muted); font-size: .82rem; }

/* Text editors */
.base64-editor-grid,
.base64-file-grid,
.base64-about-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: var(--base64-layout-gap); }
.base64-editor-pane { min-width: 0; }
.base64-editor-heading { display: flex; justify-content: space-between; align-items: center; gap: 12px; margin-bottom: 7px; }
.base64-editor-heading > label { font-weight: 700; }
.base64-editor-heading > div { display: flex; gap: 12px; color: var(--base64-muted); font-size: .8rem; }

.base64-textarea,
.base64-input {
  width: 100%;
  border: var(--base64-border-width) solid var(--base64-border-strong);
  border-radius: var(--base64-radius-control);
  background: var(--base64-control-bg);
  color: var(--base64-text);
  font: 14px/1.55 var(--base64-font-code);
}
.base64-textarea { min-height: var(--base64-editor-min-height); padding: 12px; resize: vertical; }
.base64-input { min-height: var(--base64-input-min-height); padding: 8px 10px; }
.base64-textarea[readonly] { background: var(--base64-control-subtle-bg); }

/* Actions, focus, and status */
.base64-button {
  min-height: var(--base64-control-min-height);
  padding: 7px 14px;
  border: var(--base64-border-width) solid var(--base64-border);
  border-radius: var(--base64-radius-control);
  background: var(--base64-control-subtle-bg);
  color: var(--base64-text);
  font: inherit;
  font-weight: 650;
  cursor: pointer;
}
.base64-button:hover:not(:disabled) {
  border-color: var(--base64-border-strong);
  background: var(--base64-control-hover-bg);
}

.base64-button--primary {
  border-color: var(--base64-primary);
  background: var(--base64-primary);
  color: var(--base64-on-primary);
}

.base64-button--primary:hover:not(:disabled) {
  border-color: var(--base64-primary-hover);
  background: var(--base64-primary-hover);
}

.base64-button:disabled {
  opacity: .48;
  cursor: not-allowed;
}

.base64-button:focus-visible,
.base64-mode-tab:focus-visible,
.base64-textarea:focus-visible,
.base64-input:focus-visible,
.base64-drop-zone:focus-visible {
  outline: 3px solid color-mix(in srgb, var(--base64-focus) 55%, transparent);
  outline-offset: 2px;
}

.base64-action-row { margin-top: 14px; }
.base64-size-stats { display: grid; grid-template-columns: 1fr auto 1fr 1fr; gap: 8px; margin: 14px 0 0; }
.base64-size-stats > div { padding: 10px 12px; border: var(--base64-border-width) solid var(--base64-border); border-radius: var(--base64-radius-control); background: var(--base64-soft); }
.base64-size-stats dt { color: var(--base64-muted); font-size: .8rem; }
.base64-size-stats dd { margin: 3px 0 0; font-weight: 700; }
.base64-size-stats .base64-size-arrow { align-self: center; padding: 0; border: 0; background: none; color: var(--base64-muted); }

.base64-message {
  min-height: 44px;
  margin: 14px 0 0;
  padding: 11px 13px;
  border: var(--base64-border-width) solid var(--base64-border);
  border-radius: var(--base64-radius-control);
  background: var(--base64-soft);
}

.base64-message[data-type="success"] {
  color: var(--base64-success);
  border-color: var(--base64-success-border);
  background: var(--base64-success-bg);
}

.base64-message[data-type="warning"] {
  color: var(--base64-warning);
  border-color: var(--base64-warning-border);
  background: var(--base64-warning-bg);
}

.base64-message[data-type="error"] {
  color: var(--base64-error);
  border-color: var(--base64-error-border);
  background: var(--base64-error-bg);
}

/* File converter */
.base64-file-grid > section { min-width: 0; padding: 15px; border: var(--base64-border-width) solid var(--base64-border); border-radius: var(--base64-radius-section); background: var(--base64-soft); }
.base64-drop-zone {
  display: grid;
  place-items: center;
  gap: 8px;
  min-height: 170px;
  padding: 20px;
  border: 2px dashed var(--base64-border-strong);
  border-radius: var(--base64-radius-section);
  background: var(--base64-control-bg);
  text-align: center;
  cursor: pointer;
}

.base64-drop-zone.is-dragging {
  border-color: var(--base64-primary);
  background: var(--base64-drag-bg);
}
.base64-file-info { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 8px; margin: 12px 0; }
.base64-file-info > div { min-width: 0; padding: 9px; border: var(--base64-border-width) solid var(--base64-border); border-radius: var(--base64-radius-compact); background: var(--base64-control-bg); }
.base64-file-info dt { color: var(--base64-muted); font-size: .75rem; }
.base64-file-info dd { overflow-wrap: anywhere; margin: 3px 0 0; font-weight: 650; }
.base64-output-options { margin: 13px 0; }
.base64-help { color: var(--base64-muted); font-size: .9rem; }
.base64-form-grid { display: grid; gap: 11px; margin: 14px 0; }
.base64-form-grid label { display: grid; gap: 5px; font-weight: 650; }
.base64-preview { margin-top: 15px; padding: 12px; border: var(--base64-border-width) solid var(--base64-border); border-radius: var(--base64-radius-control); background: var(--base64-control-bg); }
.base64-preview img { display: block; max-width: 100%; max-height: 360px; margin: 0 auto; object-fit: contain; }

/* Tool information */
.base64-about { line-height: 1.75; }
.base64-about-grid > div { padding: 4px 14px 4px 0; }
.base64-about li + li { margin-top: 5px; }
.base64-privacy { padding: 12px 14px; border: var(--base64-border-width) solid var(--base64-info-border); border-radius: var(--base64-radius-control); background: var(--base64-info-bg); color: var(--base64-info); }
.base64-visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  clip-path: inset(50%);
  white-space: nowrap;
  border: 0;
}

/* Responsive layout */
@media (max-width: 780px) {
  .base64-main { width: min(100% - var(--base64-page-gutter-mobile), var(--base64-content-max-width)); padding-top: 18px; }
  .base64-panel { padding: 14px; }
  .base64-panel-heading { flex-direction: column; }
  .base64-mode-tabs { width: 100%; }
  .base64-editor-grid,
  .base64-file-grid,
  .base64-about-grid { grid-template-columns: 1fr; }
  .base64-shortcut { width: 100%; margin-left: 0; }
  .base64-size-stats { grid-template-columns: 1fr 1fr 1fr; }
  .base64-size-stats .base64-size-arrow { display: none; }
  .base64-file-info { grid-template-columns: 1fr; }
}

@media (max-width: 520px) {
  .base64-toolbar { align-items: flex-start; }
  .base64-fieldset { align-items: flex-start; }
  .base64-fieldset legend { float: none; width: 100%; margin: 0; }
  .base64-action-row .base64-button { flex: 1 1 calc(50% - 8px); }
  .base64-size-stats { grid-template-columns: 1fr; }
}