:root {
  --massing-paper: #f3f1ea;
  --massing-paper-rgb: 243, 241, 234;
  --massing-ink-rgb: 36, 35, 31;
  --massing-ink: #24231f;
  --massing-accent: #ef5b2a;
}

* {
  box-sizing: border-box;
}

html,
body {
  width: 100%;
  height: 100%;
  margin: 0;
  overflow: hidden;
  background: var(--massing-paper);
  color: var(--massing-ink);
}

body {
  font-family: 'Urbanist', Arial, sans-serif;
}

#suduBar,
html.dm #suduBar {
  --ground: var(--massing-paper);
  --ink: var(--massing-ink);
  color: var(--massing-ink) !important;
}

button,
a {
  -webkit-tap-highlight-color: transparent;
}

.massing-study {
  position: fixed;
  inset: 0;
  overflow: hidden;
  background: var(--massing-paper);
  user-select: none;
  -webkit-user-select: none;
}

.massing-header {
  position: fixed;
  top: 0;
  right: 0;
  left: 0;
  z-index: 120;
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 16px;
  padding: 34px clamp(20px, 4.5vw, 64px) 30px;
  pointer-events: none;
}

.massing-mark {
  pointer-events: auto;
}

.massing-mark img {
  display: block;
  width: auto;
  height: 38px;
}

.massing-header h1 {
  margin: 0;
  padding-bottom: 2px;
  font-size: 13px;
  font-weight: 500;
  line-height: 1.4;
  letter-spacing: 0;
}

.massing-instruction,
.massing-note,
.massing-loading {
  position: fixed;
  z-index: 20;
  font-size: 10.5px;
  font-weight: 500;
  letter-spacing: .055em;
  color: rgba(var(--massing-ink-rgb), .72);
}

.massing-instruction {
  left: clamp(20px, 4.5vw, 64px);
  bottom: 30px;
  margin: 0;
}

.massing-note {
  right: clamp(20px, 4.5vw, 64px);
  bottom: 30px;
  display: flex;
  align-items: center;
  gap: 10px;
}

#massing-selection {
  max-width: 112px;
  overflow: hidden;
  color: rgba(var(--massing-ink-rgb), .58);
  text-overflow: ellipsis;
  white-space: nowrap;
}

.massing-action,
#again {
  padding: 0;
  border: 0;
  border-bottom: 1px solid rgba(var(--massing-ink-rgb), .42);
  background: transparent;
  color: inherit;
  font: inherit;
  letter-spacing: inherit;
  cursor: pointer;
}

.massing-action:hover:not(:disabled),
.massing-action:focus-visible:not(:disabled),
#again:hover,
#again:focus-visible {
  color: #111;
  border-bottom-color: #111;
  outline: none;
}

.massing-action:disabled {
  border-bottom-color: transparent;
  opacity: .22;
  cursor: default;
}

#massing-stage {
  position: absolute;
  top: 0;
  right: clamp(224px, 19vw, 272px);
  bottom: 0;
  left: 0;
  cursor: grab;
  touch-action: none;
}

#massing-stage.is-hovering {
  cursor: pointer;
}

#massing-stage.is-dragging,
#massing-stage.is-orbiting {
  cursor: grabbing;
}

#massing-stage canvas {
  display: block;
  width: 100%;
  height: 100%;
}

.massing-loading {
  top: 50%;
  left: 50%;
  margin: 0;
  transform: translate(-50%, -50%);
}

@media (max-width: 760px) {
  .massing-note {
    max-width: calc(100vw - 40px);
    gap: 8px;
  }

  #massing-selection,
  #massing-down,
  #massing-view {
    display: none;
  }

  .massing-action {
    min-height: 24px;
    padding: 4px 1px 2px;
  }
}

@media (max-width: 480px) {
  .massing-header {
    padding-top: 24px;
    padding-bottom: 22px;
  }

  .massing-mark img {
    height: 32px;
  }

  .massing-header h1 {
    font-size: 12px;
  }

  .massing-instruction,
  .massing-note {
    bottom: 22px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .massing-action {
    transition: none;
  }
}


.challenge-ledger {
  position: fixed;
  top: 96px;
  right: clamp(20px, 4.5vw, 64px);
  bottom: 68px;
  z-index: 90;
  display: grid;
  width: clamp(192px, 16vw, 226px);
  min-height: 420px;
  grid-template-rows: auto auto 154px auto auto auto;
  align-content: stretch;
  padding-left: 18px;
  border-left: 1px solid rgba(var(--massing-ink-rgb), .18);
  color: var(--massing-ink);
  pointer-events: auto;
}

.challenge-ledger button {
  border: 0;
  border-radius: 0;
  background: transparent;
  color: inherit;
  font: inherit;
  cursor: pointer;
}

.challenge-ledger button:focus-visible {
  outline: 1px solid var(--massing-accent);
  outline-offset: 3px;
}

.challenge-ledger__head,
.challenge-meta,
.challenge-actions {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.challenge-ledger__tools {
  display: flex;
  align-items: center;
  gap: 12px;
}

.challenge-score {
  color: rgba(var(--massing-ink-rgb), .46);
  font-size: 10px;
  font-weight: 500;
  letter-spacing: .055em;
}

.challenge-ledger__head {
  padding-bottom: 12px;
  font-size: 11px;
  font-weight: 600;
  letter-spacing: .08em;
  text-transform: uppercase;
}

#challenge-free {
  padding: 0 0 1px;
  border-bottom: 1px solid rgba(var(--massing-ink-rgb), .36);
  font-size: 10.5px;
  letter-spacing: .055em;
  text-transform: lowercase;
}

#challenge-free[aria-pressed="true"] {
  border-bottom-color: var(--massing-accent);
  color: var(--massing-accent);
}

.challenge-numbers {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  border-top: 1px solid rgba(var(--massing-ink-rgb), .18);
  border-left: 1px solid rgba(var(--massing-ink-rgb), .18);
}

.challenge-numbers button {
  min-height: 34px;
  border-right: 1px solid rgba(var(--massing-ink-rgb), .18);
  border-bottom: 1px solid rgba(var(--massing-ink-rgb), .18);
  font-size: 10.5px;
  font-weight: 500;
  letter-spacing: .04em;
}

.challenge-numbers button:hover,
.challenge-numbers button[aria-selected="true"] {
  color: var(--massing-accent);
}

.challenge-numbers button[aria-selected="true"] {
  box-shadow: inset 0 -2px 0 var(--massing-accent);
}

.challenge-numbers button.is-complete::after {
  display: block;
  width: 3px;
  height: 3px;
  margin: 2px auto -5px;
  border-radius: 50%;
  background: var(--massing-accent);
  content: '';
}

.challenge-preview {
  position: relative;
  min-height: 0;
  overflow: hidden;
  border-bottom: 1px solid rgba(var(--massing-ink-rgb), .18);
}

.parts-tray {
  display: none;
}

.challenge-preview canvas {
  display: block;
  width: 100%;
  height: 100%;
}

.challenge-copy {
  padding: 15px 0 13px;
  border-bottom: 1px solid rgba(var(--massing-ink-rgb), .18);
}

.challenge-meta {
  margin: 0 0 8px;
  color: rgba(var(--massing-ink-rgb), .54);
  font-size: 10px;
  font-weight: 500;
  letter-spacing: .06em;
  text-transform: uppercase;
}

.challenge-copy h2 {
  margin: 0 0 7px;
  font-size: 16px;
  font-weight: 500;
  line-height: 1.1;
  letter-spacing: -.01em;
  text-transform: uppercase;
}

.challenge-copy > p:last-child {
  max-width: 29ch;
  margin: 0;
  color: rgba(var(--massing-ink-rgb), .68);
  font-size: 12px;
  font-weight: 500;
  line-height: 1.35;
}

.challenge-actions {
  justify-content: flex-start;
  padding: 12px 0 10px;
}

.challenge-actions button {
  padding: 0 0 2px;
  border-bottom: 1px solid rgba(var(--massing-ink-rgb), .34);
  font-size: 10.5px;
  font-weight: 500;
  letter-spacing: .055em;
}

.challenge-actions button:hover,
.challenge-actions button[aria-pressed="true"] {
  border-bottom-color: var(--massing-accent);
  color: var(--massing-accent);
}

#challenge-done {
  display: inline-grid;
  width: 40px;
  height: 40px;
  flex: 0 0 40px;
  place-items: center;
  padding: 0;
  border: 1px solid rgba(var(--massing-ink-rgb), .44);
  border-radius: 50%;
  line-height: 1;
}

#challenge-done:hover,
#challenge-done:focus-visible {
  border-color: var(--massing-accent);
  color: var(--massing-accent);
}

#challenge-done:disabled {
  border-color: rgba(var(--massing-ink-rgb), .14);
  color: rgba(var(--massing-ink-rgb), .3);
  cursor: default;
}

.challenge-status {
  min-height: 15px;
  margin: 0;
  color: rgba(var(--massing-ink-rgb), .48);
  font-size: 10.5px;
  font-weight: 500;
  letter-spacing: .055em;
}

.challenge-status.is-complete {
  color: var(--massing-accent);
}

.challenge-success {
  position: fixed;
  top: 50%;
  left: calc(50% - clamp(105px, 9.5vw, 136px));
  z-index: 230;
  display: grid;
  min-width: 118px;
  justify-items: center;
  gap: 7px;
  color: var(--massing-accent);
  opacity: 0;
  transform: translate(-50%, -44%) scale(.96);
  transition: opacity .28s ease, transform .42s cubic-bezier(.22, 1, .36, 1);
  pointer-events: none;
}

.challenge-success::before {
  width: 54px;
  height: 54px;
  border: 1px solid currentColor;
  border-radius: 50%;
  content: '';
}

.challenge-success > span {
  margin-top: -41px;
  font-size: 10px;
  font-weight: 600;
  letter-spacing: .08em;
  text-transform: uppercase;
}

.challenge-success > small {
  margin-top: 25px;
  color: rgba(var(--massing-ink-rgb), .56);
  font-size: 9px;
  font-weight: 500;
  letter-spacing: .08em;
  text-transform: uppercase;
}

.challenge-success.is-visible {
  opacity: 1;
  transform: translate(-50%, -50%) scale(1);
}

@media (max-width: 900px) {
  #massing-stage {
    right: 0;
  }

  .challenge-ledger {
    top: auto;
    right: 20px;
    bottom: 64px;
    left: 20px;
    width: auto;
    min-height: 0;
    grid-template-columns: 112px minmax(0, 1fr);
    grid-template-rows: auto auto auto auto;
    column-gap: 14px;
    padding: 12px;
    border: 1px solid rgba(var(--massing-ink-rgb), .2);
    background: rgba(var(--massing-paper-rgb), .95);
    -webkit-backdrop-filter: blur(8px);
    backdrop-filter: blur(8px);
  }

  .challenge-ledger__head {
    grid-column: 1 / -1;
    padding-bottom: 8px;
  }

  .challenge-numbers {
    grid-column: 2;
    grid-row: 2;
  }

  .challenge-preview {
    grid-column: 1;
    grid-row: 2 / 5;
    min-height: 114px;
    border-bottom: 0;
    border-right: 1px solid rgba(var(--massing-ink-rgb), .18);
  }

  .challenge-copy {
    grid-column: 2;
    grid-row: 3;
    padding: 10px 0 8px;
  }

  .challenge-actions {
    grid-column: 2;
    grid-row: 4;
    padding: 8px 0 0;
  }

  .challenge-status {
    position: absolute;
    right: 12px;
    bottom: 12px;
  }
}

@media (max-width: 560px) {
  .challenge-ledger {
    right: 12px;
    bottom: 58px;
    left: 12px;
    grid-template-columns: 84px minmax(0, 1fr);
    column-gap: 10px;
    padding: 10px;
  }

  .challenge-preview {
    min-height: 98px;
  }

  .challenge-numbers button {
    min-height: 28px;
    font-size: 9.5px;
  }

  .challenge-copy {
    padding-top: 8px;
  }

  .challenge-copy h2 {
    margin-bottom: 4px;
    font-size: 14px;
  }

  .challenge-copy > p:last-child,
  #challenge-level,
  .challenge-status {
    display: none;
  }

  .challenge-actions {
    gap: 10px;
  }
}

/* The phone is a compact workbench: finite parts above, model in the middle,
   challenge and manipulation controls below. */
@media (max-width: 640px) {
  .massing-header {
    z-index: 220;
    align-items: center;
    padding: 20px 16px 14px;
    background: linear-gradient(to bottom, var(--massing-paper) 70%, rgba(var(--massing-paper-rgb), 0));
  }

  .massing-mark img {
    height: 32px;
  }

  .massing-header h1 {
    padding: 0;
    font-size: 12px;
  }

  .parts-tray {
    position: fixed;
    top: 66px;
    right: 0;
    left: 0;
    z-index: 210;
    display: grid;
    height: 76px;
    grid-template-columns: 42px minmax(0, 1fr);
    align-items: stretch;
    border-top: 1px solid rgba(var(--massing-ink-rgb), .11);
    border-bottom: 1px solid rgba(var(--massing-ink-rgb), .16);
    background: rgba(var(--massing-paper-rgb), .96);
    -webkit-backdrop-filter: blur(12px);
    backdrop-filter: blur(12px);
  }

  .parts-tray__label {
    display: grid;
    place-items: center;
    border-right: 1px solid rgba(var(--massing-ink-rgb), .13);
    color: rgba(var(--massing-ink-rgb), .52);
    font-size: 9px;
    font-weight: 600;
    letter-spacing: .07em;
    text-transform: uppercase;
    writing-mode: vertical-rl;
    transform: rotate(180deg);
  }

  .parts-tray__rail {
    display: flex;
    min-width: 0;
    overflow-x: auto;
    overflow-y: hidden;
    overscroll-behavior-x: contain;
    scroll-snap-type: x proximity;
    scrollbar-width: none;
    -webkit-overflow-scrolling: touch;
  }

  .parts-tray__rail::-webkit-scrollbar {
    display: none;
  }

  .parts-tray__part {
    position: relative;
    display: grid;
    width: 70px;
    min-width: 70px;
    height: 75px;
    grid-template-rows: 48px 1fr;
    place-items: center;
    margin: 0;
    padding: 3px 5px 5px;
    scroll-snap-align: start;
    border: 0;
    border-right: 1px solid rgba(var(--massing-ink-rgb), .12);
    border-radius: 0;
    background: transparent;
    color: var(--massing-ink);
    font-family: inherit;
    cursor: pointer;
  }

  .parts-tray__part:focus-visible {
    outline: 1px solid var(--massing-accent);
    outline-offset: -3px;
  }

  .parts-tray__part:active:not(:disabled) {
    background: rgba(var(--massing-ink-rgb), .055);
  }

  .parts-tray__part:disabled {
    opacity: .2;
  }

  .parts-tray__icon {
    display: block;
    width: 58px;
    height: 36px;
  }

  .parts-tray__name {
    align-self: start;
    width: 100%;
    overflow: hidden;
    font-size: 9px;
    font-weight: 500;
    line-height: 1;
    text-align: center;
    text-overflow: ellipsis;
    white-space: nowrap;
  }

  .parts-tray__count {
    position: absolute;
    top: 5px;
    right: 5px;
    min-width: 14px;
    color: rgba(var(--massing-ink-rgb), .52);
    font-size: 9px;
    font-weight: 600;
    text-align: center;
  }

  #massing-stage {
    inset: 0;
  }

  .massing-instruction {
    display: none;
  }

  .massing-note {
    right: 12px;
    bottom: calc(118px + env(safe-area-inset-bottom, 0px));
    left: 12px;
    z-index: 205;
    justify-content: flex-end;
    gap: 4px;
    max-width: none;
    pointer-events: none;
  }

  #massing-selection,
  #again {
    display: none;
  }

  #massing-turn,
  #massing-up,
  #massing-down,
  #massing-return,
  #massing-undo,
  #massing-view {
    display: inline-grid;
  }

  .massing-action {
    min-width: 44px;
    min-height: 40px;
    place-items: center;
    padding: 0 8px;
    border: 1px solid rgba(var(--massing-ink-rgb), .2);
    background: rgba(var(--massing-paper-rgb), .88);
    font-size: 10px;
    pointer-events: auto;
    -webkit-backdrop-filter: blur(8px);
    backdrop-filter: blur(8px);
  }

  .massing-action:disabled {
    border-color: rgba(var(--massing-ink-rgb), .09);
    opacity: .24;
  }

  .challenge-ledger {
    position: fixed;
    top: auto;
    right: 0;
    bottom: calc(52px + env(safe-area-inset-bottom, 0px));
    left: 0;
    z-index: 215;
    display: grid;
    width: auto;
    height: 62px;
    min-height: 0;
    grid-template-columns: minmax(0, 1fr) auto;
    grid-template-rows: 30px 26px;
    gap: 0 10px;
    padding: 3px 12px 1px;
    border: 0;
    border-top: 1px solid rgba(var(--massing-ink-rgb), .16);
    background: rgba(var(--massing-paper-rgb), .96);
    -webkit-backdrop-filter: blur(12px);
    backdrop-filter: blur(12px);
  }

  .challenge-ledger__head {
    grid-column: 2;
    grid-row: 1;
    justify-content: flex-end;
    padding: 0;
    margin-right: 50px;
  }

  .challenge-ledger__head > span:first-child {
    display: none;
  }

  .challenge-ledger__tools {
    gap: 10px;
  }

  .challenge-score {
    min-width: 28px;
    font-size: 9px;
    text-align: right;
  }

  #challenge-free {
    min-width: 28px;
    min-height: 28px;
    font-size: 9px;
  }

  .challenge-numbers {
    grid-column: 1;
    grid-row: 1;
    display: flex;
    min-width: 0;
    overflow-x: auto;
    border: 0;
    scrollbar-width: none;
    -webkit-overflow-scrolling: touch;
  }

  .challenge-numbers::-webkit-scrollbar {
    display: none;
  }

  .challenge-numbers button {
    width: 34px;
    min-width: 34px;
    min-height: 28px;
    border: 0;
    font-size: 9px;
    scroll-snap-align: center;
  }

  .challenge-numbers button[aria-selected="true"] {
    box-shadow: inset 0 -1px 0 var(--massing-accent);
  }

  .challenge-preview {
    position: fixed;
    right: 12px;
    bottom: calc(122px + env(safe-area-inset-bottom, 0px));
    width: 150px;
    height: 150px;
    min-height: 0;
    overflow: hidden;
    border: 1px solid rgba(var(--massing-ink-rgb), .16);
    background: rgba(var(--massing-paper-rgb), .97);
    opacity: 0;
    visibility: hidden;
    transform: translateY(8px) scale(.96);
    transform-origin: bottom right;
    transition: opacity .22s ease, transform .22s ease, visibility 0s linear .22s;
    pointer-events: none;
  }

  .challenge-ledger.is-preview-open .challenge-preview {
    opacity: 1;
    visibility: visible;
    transform: none;
    transition-delay: 0s;
  }

  .challenge-copy {
    grid-column: 1;
    grid-row: 2;
    display: flex;
    align-items: center;
    min-width: 0;
    padding: 0;
    border: 0;
  }

  .challenge-copy h2 {
    overflow: hidden;
    margin: 0;
    font-size: 12px;
    line-height: 1;
    text-overflow: ellipsis;
    white-space: nowrap;
  }

  .challenge-meta,
  .challenge-copy > p:last-child,
  .challenge-status {
    display: none;
  }

  .challenge-actions {
    grid-column: 2;
    grid-row: 2;
    align-self: center;
    gap: 10px;
    padding: 0;
    margin-right: 50px;
  }

  .challenge-actions button {
    min-height: 24px;
    padding: 0 0 1px;
    font-size: 9.5px;
  }

  #challenge-done {
    position: absolute;
    top: 9px;
    right: 12px;
    width: 44px;
    height: 44px;
    border-color: rgba(var(--massing-ink-rgb), .58);
    color: var(--massing-ink);
    font-size: 9px;
    letter-spacing: .07em;
    text-transform: uppercase;
  }

  #challenge-done:not(:disabled) {
    border-color: var(--massing-accent);
    color: var(--massing-accent);
  }

  .challenge-success {
    top: calc(50% - 3px);
    left: 50%;
  }
}

@media (prefers-reduced-motion: reduce) {
  .challenge-success {
    transition: none;
  }
}

@media (max-width: 390px) {
  .massing-action {
    min-width: 38px;
    padding-right: 5px;
    padding-left: 5px;
    font-size: 9px;
  }

  .challenge-actions {
    gap: 7px;
  }

  .challenge-actions button {
    font-size: 9px;
  }
}

@media (min-width: 641px) {
  #massing-stage {
    right: clamp(210px, 19vw, 272px);
  }

  .challenge-ledger {
    top: 96px;
    right: clamp(20px, 4.5vw, 64px);
    bottom: auto;
    left: auto;
    display: grid;
    width: clamp(184px, 15.5vw, 220px);
    height: auto;
    min-height: 0;
    grid-template-columns: minmax(0, 1fr);
    grid-template-rows: auto auto 124px auto auto auto;
    align-content: start;
    gap: 0;
    padding: 0 0 14px 16px;
    border: 0;
    border-left: 1px solid rgba(var(--massing-ink-rgb), .18);
    background: transparent;
    -webkit-backdrop-filter: none;
    backdrop-filter: none;
  }

  .challenge-ledger__head,
  .challenge-numbers,
  .challenge-preview,
  .challenge-copy,
  .challenge-actions,
  .challenge-status {
    grid-column: 1;
    position: static;
  }

  .challenge-ledger__head {
    grid-row: 1;
    padding-bottom: 10px;
  }

  .challenge-numbers {
    grid-row: 2;
    width: 160px;
    justify-self: start;
  }

  .challenge-numbers button {
    width: 32px;
    min-height: 32px;
    aspect-ratio: 1;
    padding: 0;
  }

  .challenge-preview {
    grid-row: 3;
    width: 160px;
    height: 124px;
    justify-self: start;
  }

  .challenge-copy {
    grid-row: 4;
    padding: 12px 0 10px;
  }

  .challenge-actions {
    grid-row: 5;
    gap: 8px;
    padding: 9px 0 7px;
  }

  .challenge-status {
    grid-row: 6;
    min-height: 14px;
    padding-top: 1px;
  }
}

/* The complete workbench follows the website ground selection. */
html.dm {
  --massing-paper: var(--dm-bg, #121110);
  --massing-paper-rgb: 18, 17, 16;
  --massing-ink: #f5f3ec;
  --massing-ink-rgb: 245, 243, 236;
}
html.dm.dmwarm {
  --massing-paper-rgb: 192, 67, 31;
  --massing-accent: #f5f3ec;
}
html.dm .massing-mark img { filter: invert(1); }
html.dm .massing-action:hover:not(:disabled), html.dm #again:hover { color: var(--massing-ink); border-color: currentColor; }