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Cart Drawer UI Patterns: 9 Motion Techniques

· Godrich · 9 items · 33 min read

TransitionsSCSSVanilla JSClickAutoplayCheckoutNavigation

One panel overshoots its open position before a spring curve settles it, one drag distance meets growing resistance past a threshold, and a badge number closes

Slide overshoot — a cart panel whose open position value passes its target before settling back01 cart-drawer-slide-spring-overshoot Backdrop scale-back — the page behind shrinks in proportion to how far the panel has opened02 cart-drawer-backdrop-depth-scale Item stagger cascade — each row's delay grows with its position value in the list03 cart-drawer-item-stagger-cascade Elastic quantity bump — a quantity number that grows then eases back by the size of its change04 cart-drawer-qty-bump-elastic Rubber-band drag close — a drag distance value that meets growing resistance past a threshold05 cart-drawer-swipe-dismiss-rubberband Empty-state crossfade — a message that fades out the instant the item count value leaves zero06 cart-drawer-empty-state-crossfade Checkout bar lift — a bottom bar whose shadow and height values grow with scroll position07 cart-drawer-sticky-checkout-reveal Remove-item collapse — a removed row's height value shrinking to zero as rows below close the gap08 cart-drawer-remove-item-collapse Badge count inertia — a number on the icon that eases toward a changed value frame by frame09 cart-drawer-badge-count-inertia

Auto-plays · click a tile to jump to its section · all nine in one zip

None of the nine ever process a real order — the checkout bar in 07 and the drawer's own open state only ever transition locally, and nothing here calls fetch or submits a payment; every product name and price is invented, and zero real brand appears anywhere in the set. All nine also answer something a visitor actually does: 01, 02, 03, 04, 06, 08, and 09 each answer a real click, 05 answers pointerdown, pointermove, and pointerup together as a single drag, and 07 answers wheel, pointerdown, scroll, and resize — not one of the nine only plays on autoplay.

Anatomy of nine patterns — when position, distance, and count values recompute

Nine patterns split into three ways of turning a click, a drag, or an item count into a value worth animating, and skipping this layer is what makes a cart drawer ui pattern read as a handful of disconnected transitions instead of nine small calculators.

Why three patterns tween a fixed 0-to-1 progress value against a duration constant

02, 06, and 08 each start a requestAnimationFrame loop the instant a state flips — the drawer opens, the item count leaves zero, or a row gets removed — and divide elapsed time by a duration constant to get a progress value between 0 and 1 that an easing function then reshapes. 02's easeInOutCubic turns that progress into a paired scale and brightness value for the page behind the panel. 06 runs the same easing function toward the opposite goal, turning progress into two opacity values that cross as one rises and the other falls. 08 uses easeInCubic instead, so a removed row's height, opacity, and horizontal offset all start shrinking slowly and accelerate as the row finishes collapsing.

Why three patterns solve a decay or resistance formula directly from elapsed time or drag distance

01, 04, and 05 never touch a bounded progress ratio at all — each one solves a closed-form equation instead. 01's springProgress plugs elapsed time straight into a damped harmonic oscillator equation, so the position value can pass 1 and swing back before settling, something an easing curve alone cannot produce. 04's elasticPulse solves a decaying sine wave of elapsed time for the quantity number's size, while a second function, easeOutCubic, separately grows and fades a ripple around it. 05's rubberband takes live drag distance, not time, and compresses it through an exponential formula the instant a pointer moves past a threshold.

Why three patterns keep recomputing a value that chases a moving target instead of completing

03, 07, and 09 never reach a final resting value the way a tween does — each one keeps recomputing against a target that itself keeps changing. 03's computeDelay divides a fixed total spread time by the current row count every time the list reorders, so a delay value is a function of position, not a fixed per-row number. 07's lerp closes part of the gap between a shadow value and a scroll-derived target on every tick, so the target itself moves as a visitor scrolls. 09's lerp does the same for a badge number, closing part of the remaining difference every frame until the displayed number catches the target count.

Code per pattern — how does each value get computed?

01Slide overshoot — a cart panel whose open position value passes its target before settling back

Once the panel enters its open state, its position value follows a spring curve that overshoots the target slightly before settling, and once it closes that value retreats along the same curve in reverse.

Slide overshoot — a cart panel whose open position value passes its target before settling back
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01 · Slide overshoot — a cart panel whose open position value passes its target before settling back — Measured area 100.0% · moving frames 19/23Original by GODRICH · SCSS and React ship in the zip · See the password

ZETAOMEGAspringProgress

What the numbers say

Across 23 tracked frames, 01 moves on 19 of them, covering 100.0% cumulative area at a 165.3 average intensity — the highest area score of the nine, because an underdamped spring keeps repainting the panel's transform well past the moment a plain slide-in would have already stopped. ZETA sets how quickly that motion decays and OMEGA sets how fast it oscillates while decaying, and springProgress is what turns those two constants and elapsed time into the single position value apply writes to the panel's transform and the backdrop's opacity.

  // calc layer: solves a damped harmonic oscillator (spring) equation directly every frame to build the position value —
  // not borrowing an easing curve, but computing a value that overshoots the target and returns, driven by the damping ratio (ZETA) and natural frequency (OMEGA).
  var ZETA = 0.42;
  var OMEGA = 9.5;
  var OMEGA_D = OMEGA * Math.sqrt(1 - ZETA * ZETA);
  function springProgress(tSec) {
    if (tSec <= 0) { return 0; }
    var env = Math.exp(-ZETA * OMEGA * tSec);
    return 1 - env * (Math.cos(OMEGA_D * tSec) + (ZETA * OMEGA / OMEGA_D) * Math.sin(OMEGA_D * tSec));
  }

  var DURATION_S = 0.85;
  var isOpen = false;
  var raf = null;

  function apply(v) {
    var pct = (1 - v) * 100;
    panel.style.transform = 'translateX(' + pct.toFixed(2) + '%)';
    backdrop.style.opacity = Math.min(1, Math.max(0, v)).toFixed(3);
  }

02Backdrop scale-back — the page behind shrinks in proportion to how far the panel has opened

As the panel's open progress value increases, the page behind it shrinks and dims by a matched amount so the panel appears to float forward, and both values reverse at the same rate as it closes.

Backdrop scale-back — the page behind shrinks in proportion to how far the panel has opened
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02 · Backdrop scale-back — the page behind shrinks in proportion to how far the panel has opened — Measured area 55.719% · moving frames 15/23Original by GODRICH · SCSS and React ship in the zip · See the password

MIN_SCALEMAX_DIMeaseInOutCubic

What the numbers say

02 moves on 15 of 23 frames, covering 55.719% cumulative area at a 133.1 average intensity, since every tick that updates the panel also has to repaint the full-page backdrop behind it. MIN_SCALE sets the floor the page's scale value shrinks toward and MAX_DIM sets how far its brightness value falls, while easeInOutCubic is the one function that reshapes a single progress number into both the scale and the dim value at once, so they can never visibly drift out of step with each other.

  // calc layer: interpolates the panel's open progress value (0-1) through an easing function to compute the page-behind's
  // scale value and dim value at the same rate — deriving both from one value instead of animating scale and filter separately.
  function easeInOutCubic(p) {
    return p < 0.5 ? 4 * p * p * p : 1 - Math.pow(-2 * p + 2, 3) / 2;
  }

  var DURATION_S = 0.5;
  var MIN_SCALE = 0.86;
  var MAX_DIM = 0.5;
  var isOpen = false;
  var raf = null;

  function apply(progress) {
    var eased = easeInOutCubic(Math.min(1, Math.max(0, progress)));
    var scale = 1 - eased * (1 - MIN_SCALE);
    var dim = eased * MAX_DIM;
    page.style.transform = 'scale(' + scale.toFixed(4) + ')';
    page.style.filter = 'brightness(' + (1 - dim).toFixed(3) + ')';
    panel.style.transform = 'translateX(' + ((1 - eased) * 100).toFixed(2) + '%)';
  }

03Item stagger cascade — each row's delay grows with its position value in the list

Once the panel opens, each row receives a delay value proportional to its position in the list so rows appear top to bottom in sequence, and when items are reordered that delay value is recomputed for the new order.

Item stagger cascade — each row's delay grows with its position value in the list
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03 · Item stagger cascade — each row's delay grows with its position value in the list — Measured area 29.915% · moving frames 10/23Original by GODRICH · SCSS and React ship in the zip · See the password

computeDelayTOTAL_SPREAD_MSBASE_MS

What the numbers say

03 moves on 10 of 23 frames, covering 29.915% cumulative area at a 96.6 average intensity, a mid-range score that reflects rows entering once each rather than repainting continuously like a tween. BASE_MS sets the smallest delay any row can get and TOTAL_SPREAD_MS sets the full window every row's delay has to fit inside, and computeDelay divides that window by the current row count so a four-item cart drawer and a two-item one both finish their cascade in the same total time.

  var NAMES = ['Puffer Vest', 'Knit Gloves', 'Check Scarf', 'Winter Boots'];

  // calc layer: divides the total spread time (TOTAL_SPREAD_MS) by the current item count to recompute each row's delay value
  // (computeDelay()) — once the order changes, every position's delay value is recomputed under the same rule.
  var BASE_MS = 40;
  var TOTAL_SPREAD_MS = 480;

  function computeDelay(indexInOrder, total) {
    var steps = Math.max(1, total - 1);
    var perStep = TOTAL_SPREAD_MS / steps;
    return BASE_MS + indexInOrder * perStep;
  }

  var order = NAMES.map(function (_, i) { return i; });

  function render() {
    list.textContent = '';
    order.forEach(function (nameIndex, pos) {
      var li = document.createElement('li');
      li.className = 'cdis__row';
      li.style.setProperty('--delay', computeDelay(pos, order.length) + 'ms');
      li.textContent = NAMES[nameIndex];
      list.appendChild(li);
    });
  }

04Elastic quantity bump — a quantity number that grows then eases back by the size of its change

Once the quantity value changes, the number's size value grows in proportion to the change before easing back along an elastic curve, and a decreasing value dips slightly smaller before returning the same way.

Elastic quantity bump — a quantity number that grows then eases back by the size of its change
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04 · Elastic quantity bump — a quantity number that grows then eases back by the size of its change — Measured area 8.746% · moving frames 16/23Original by GODRICH · SCSS and React ship in the zip · See the password

elasticPulseAMPLITUDEapplyRipple

What the numbers say

04 moves on 16 of 23 frames but covers only 8.746% cumulative area at a 45.1 average intensity, the lowest intensity of the nine, because the moving region is just the quantity number and a small ripple rather than a full panel or page. AMPLITUDE, FREQ, and DECAY are the three constants elasticPulse combines into a decaying sine wave for the number's scale, while applyRipple runs a completely separate easeOutCubic curve on the same elapsed time to grow and fade a ring around it — two values from one clock, not one value reused twice.

  // calc layer: computes a decaying sine wave (elasticPulse()) every frame from the elapsed time (t) since the value changed
  // and assigns it to scale — solved fresh from the moment the value changed, not a fixed percentage curve from CSS keyframes.
  var AMPLITUDE = 0.3;
  var FREQ = 18;
  var DECAY = 9;
  function elasticPulse(tSec) {
    if (tSec <= 0) { return 1; }
    return 1 + AMPLITUDE * Math.sin(tSec * FREQ) * Math.exp(-DECAY * tSec);
  }

  // calc layer 2: separately from the bump, the ripple around the badge grows its radius on an ease-out curve
  // while fading at the same time — pulling both scale and opacity from one progress value (p), the same pattern as the depth-scale item, on a different target.
  function easeOutCubic(p) { return 1 - Math.pow(1 - p, 3); }
  var rippleEl = document.getElementById('cqbeRipple');
  function applyRipple(tSec) {
    var p = Math.min(1, Math.max(0, tSec / 0.5));
    var eased = easeOutCubic(p);
    var s = 0.4 + eased * 2.1;
    var op = (1 - eased) * 0.4;
    rippleEl.style.transform = 'translate(-50%, -50%) scale(' + s.toFixed(3) + ')';
    rippleEl.style.opacity = op.toFixed(3);
  }

05Rubber-band drag close — a drag distance value that meets growing resistance past a threshold

As the drag distance value increases, the panel's movement follows a resistance curve where the ratio of travel shrinks, and once that distance value crosses a threshold the remaining distance value collapses at once to the closed position.

Rubber-band drag close — a drag distance value that meets growing resistance past a threshold
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05 · Rubber-band drag close — a drag distance value that meets growing resistance past a threshold — Measured area 8.522% · moving frames 16/23Original by GODRICH · SCSS and React ship in the zip · See the password

rubberbandTHRESHOLDMAX_PULL

What the numbers say

05 moves on 16 of 23 frames, covering 8.522% cumulative area at a 161.6 average intensity, the second-highest intensity of the nine — the visible region stays small but changes sharply every frame a pointer is dragging. THRESHOLD marks where the resistance curve begins and MAX_PULL caps how much extra travel the exponential formula inside rubberband will ever add past that point, so a card can be pulled indefinitely far without ever visually leaving the drawer.

  // calc layer: once the drag distance passes a threshold, a resistance function (rubberband()) compresses the travel amount —
  // a real rubber-band formula (the same family as iOS overscroll) where the ratio reflected on screen shrinks the further it's pulled,
  // not a simple clamp.
  var THRESHOLD = 90;
  var MAX_PULL = 140;
  function rubberband(dx) {
    var sign = dx < 0 ? -1 : 1;
    var abs = Math.abs(dx);
    if (abs <= THRESHOLD) { return dx; }
    var over = abs - THRESHOLD;
    var compressed = MAX_PULL * (1 - Math.exp(-over / MAX_PULL));
    return sign * (THRESHOLD + compressed);
  }

  var dragging = false;
  var startX = 0;
  var current = 0;

  function apply(dx) {
    var x = rubberband(dx);
    card.style.transform = 'translateX(' + x.toFixed(2) + 'px)';
    var trashOpacity = Math.min(1, Math.abs(x) / THRESHOLD);
    row.style.setProperty('--trash-opacity', trashOpacity.toFixed(3));
  }

06Empty-state crossfade — a message that fades out the instant the item count value leaves zero

While the item count value stays at zero, the message keeps its opacity value, and once that count value moves to one or more, the message's opacity value falls as the list's opacity value rises in a crossing pair.

Empty-state crossfade — a message that fades out the instant the item count value leaves zero
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06 · Empty-state crossfade — a message that fades out the instant the item count value leaves zero — Measured area 14.408% · moving frames 8/23Original by GODRICH · SCSS and React ship in the zip · See the password

crossfadeApplyDUR_MSframe

What the numbers say

06 moves on only 8 of 23 frames, covering 14.408% cumulative area at a 74.6 average intensity, because the crossfade only ever runs once per direction — the moment the count crosses zero, not on every tick after. DUR_MS sets how long that single crossfade takes, and crossfadeApply is what keeps the two opacity values complementary: it computes one directly from the eased progress and derives the other by subtracting from 1, so the list and the empty message are never both fully visible at once.

  // calc layer: eases a single progress value (p, 0-1) to compute both states' opacity in opposite directions at the same time
  // (crossfadeApply()) — deriving both complementarily from one value instead of running two separate animations.
  function easeInOutCubic(p) {
    return p < 0.5 ? 4 * p * p * p : 1 - Math.pow(-2 * p + 2, 3) / 2;
  }
  var DUR_MS = 420;
  var hasItems = false;
  var raf = null;

  function crossfadeApply(p, toItems) {
    var eased = easeInOutCubic(p);
    var itemsOpacity = toItems ? eased : 1 - eased;
    var emptyOpacity = 1 - itemsOpacity;
    listEl.style.opacity = itemsOpacity.toFixed(3);
    listEl.style.transform = 'scale(' + (0.96 + itemsOpacity * 0.04).toFixed(3) + ')';
    emptyEl.style.opacity = emptyOpacity.toFixed(3);
    emptyEl.style.transform = 'scale(' + (0.96 + emptyOpacity * 0.04).toFixed(3) + ')';
  }

07Checkout bar lift — a bottom bar whose shadow and height values grow with scroll position

Once the list's scroll position value nears the bottom, the bottom bar's shadow depth value and height value both grow so it lifts forward, and as the scroll position value moves back up both values shrink to their resting size.

Checkout bar lift — a bottom bar whose shadow and height values grow with scroll position
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07 · Checkout bar lift — a bottom bar whose shadow and height values grow with scroll position — Measured area 8.047% · moving frames 23/23Original by GODRICH · SCSS and React ship in the zip · See the password

lerpCYCLE_MScomputeMax

What the numbers say

07 is the only item in this set that moves on all 23 of 23 tracked frames, though it covers just 8.047% cumulative area at a 110.1 average intensity — a shadow's opacity and a small transform change on almost every tick, but never across a large region. lerp closes part of the gap between the current shadow value and a target computed fresh each tick from scrollTop, and computeMax recomputes the scrollable range itself from scrollHeight and clientHeight rather than assuming a fixed list length.

  // calc layer: interpolates the scroll progress (0-1) into the shadow intensity and bar height values every frame via lerp() —
  // not using the scroll position directly, but an inertial interpolation that closes toward the target value a little each frame.
  function lerp(a, b, t) { return a + (b - a) * t; }

  var maxScroll = 1;
  function computeMax() {
    maxScroll = Math.max(1, scrollEl.scrollHeight - scrollEl.clientHeight);
  }

  var shadow = 0;
  var raf = null;
  function tick() {
    var target = Math.min(1, scrollEl.scrollTop / maxScroll);
    shadow = lerp(shadow, target, 0.18);
    bar.style.setProperty('--shadow-op', shadow.toFixed(3));
    bar.style.transform = 'translateY(' + (-shadow * 2).toFixed(2) + 'px)';
    if (Math.abs(target - shadow) > 0.002) {
      raf = requestAnimationFrame(tick);
    } else {
      raf = null;
    }
  }

08Remove-item collapse — a removed row's height value shrinking to zero as rows below close the gap

Once a row is removed, its height value shrinks to zero while the rows below follow with a matching position value that closes the gap, and once that value reaches zero the row leaves the list.

Remove-item collapse — a removed row's height value shrinking to zero as rows below close the gap
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08 · Remove-item collapse — a removed row's height value shrinking to zero as rows below close the gap — Measured area 26.947% · moving frames 8/23Original by GODRICH · SCSS and React ship in the zip · See the password

collapseRoweaseInCubicSTOCK

What the numbers say

08 moves on 8 of 23 frames, covering 26.947% cumulative area at a 47.6 average intensity — the area score is mid-range because a full row's height, opacity, and horizontal offset shrink together, but it only happens once per removal rather than continuously. DUR_MS sets how long that single collapse takes and easeInCubic shapes the row's height so it starts slow and finishes fast, while refillIfEmpty calls a fixed STOCK array to replace a removed row the moment fewer than two remain in the list.

  function collapseRow(row) {
    var h = row.getBoundingClientRect().height;
    row.style.overflow = 'hidden';
    row.style.height = h + 'px';
    row.style.willChange = 'height, opacity, transform';
    var start = performance.now();
    function frame(now) {
      var p = Math.min(1, (now - start) / DUR_MS);
      var eased = easeInCubic(p);
      row.style.height = (h * (1 - eased)) + 'px';
      row.style.opacity = String(1 - eased);
      row.style.transform = 'translateX(' + (-eased * 24) + 'px)';
      if (p < 1) {
        requestAnimationFrame(frame);
      } else {
        row.remove();
        refillIfEmpty();
      }
    }
    requestAnimationFrame(frame);
  }

09Badge count inertia — a number on the icon that eases toward a changed value frame by frame

Once the item count value changes, the number on the icon doesn't jump straight to it — each frame it closes only part of the remaining difference value until it arrives, and its size value briefly grows then shrinks along the way.

Badge count inertia — a number on the icon that eases toward a changed value frame by frame
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09 · Badge count inertia — a number on the icon that eases toward a changed value frame by frame — Measured area 0.232% · moving frames 22/23Original by GODRICH · SCSS and React ship in the zip · See the password

lerptargetdisplayed

What the numbers say

09 moves on 22 of 23 frames but covers just 0.232% cumulative area at a 70.4 average intensity, the smallest area score of the nine, since only a small badge and a single digit ever change. The same lerp function from 07 reappears here closing part of the gap between displayed and target every frame at a fixed rate, and a pulse value derived from how far apart those two numbers still are briefly enlarges the badge while it's catching up.

  // calc layer: the displayed number (displayed) catches up toward the target number (target) every frame via an inertial lerp() —
  // instead of recounting whenever the value changes, it shrinks the gap between the two values a little each frame.
  function lerp(a, b, t) { return a + (b - a) * t; }

  var target = 0;
  var displayed = 0;
  var raf = null;

  function tick() {
    displayed = lerp(displayed, target, 0.16);
    var shown = Math.round(displayed);
    badge.textContent = String(shown);
    var pulse = 1 + Math.min(0.3, Math.abs(target - displayed) / (target + 1) * 0.6);
    badge.style.transform = 'scale(' + pulse.toFixed(3) + ')';
    if (Math.abs(target - displayed) > 0.03) {
      raf = requestAnimationFrame(tick);
    } else {
      displayed = target;
      badge.textContent = String(target);
      badge.style.transform = 'scale(1)';
      raf = null;
    }
  }

Where values reshape a pattern — overshoot factor, resistance curve, delay value

Swap out the value a pattern is built on and the interaction it produces shifts with it, even though the markup underneath never changes — this is the difference a drawer panel's feel actually lives or dies on.

Why 01's damping ratio decides how many times the panel overshoots before settling

ZETA is not a duration — it's a damping ratio, and reading it that way is what explains why the panel can pass its target and swing back rather than simply arriving late. A value close to 1 barely overshoots at all, while a lower value lets the underdamped term in springProgress dominate for longer, producing two or three visible swings before the position value settles inside the resting range.

Why 05's threshold distance decides where resistance begins, not how strong it becomes

THRESHOLD only marks the distance at which rubberband switches from returning dx unchanged to compressing it — it has no effect on how much resistance a pull past that point actually feels, since MAX_PULL alone controls how far the compressed value can still travel. Reading THRESHOLD as a starting line rather than a strength dial is what keeps a short drag feeling identical regardless of where the resistance curve begins.

Why 03's delay value has to be recomputed from position, not assigned once per row

Assigning a fixed delay to each row by name would break the moment the cart reorders, since computeDelay only produces a coherent cascade when it divides the current total spread time by the row's live index in order. Reading the delay as a value tied to position rather than identity is what lets the same four constants keep working after the demo's own reorder button runs.

Where it breaks — fast drags, quantity spikes, an empty cart

Where this set differs from 9 CSS Sidebar Animations — Minimal JS, Checkout Page Design — 9 Cart Patterns, No Library, and 9 Filter UI Patterns (Panel Slide to Chip Remove) is which value each set's panel actually recomputes. That sidebar set recomputes a slide offset from a fixed open-or-closed state, not a spring value that can overshoot its own target. The checkout set recomputes a step index across a multi-page flow rather than a single panel's position or drag value. The filter set recomputes a chip's removal from a click, but never a drag distance compressed through resistance the way 05 does here. Every one of these nine computations, unlocked with gnavhgub, ships ready to drop into a real cart drawer website.

What a fast, short drag does to 05's dismiss decision

onUp only checks Math.abs(current) > THRESHOLD * 1.3 — a final distance, not a speed — so a fast flick that releases before the card has actually traveled past that distance snaps right back to center exactly like a slow, hesitant one would. A real product wants both signals: this demo shows why distance alone is easy to reach for, and where a velocity check would need to be added alongside it.

What happens once a count target passes nine in 09

addOne adds one to target and then checks if (target > 9) { target = 0; displayed = 0; badge.textContent = '0'; }, so once a tenth item would arrive the badge silently resets to zero instead of showing a capped "9+" the way many real cart icons do. Because lerp only ever eases toward whatever target currently holds, it eases toward zero here exactly as smoothly as it eases toward any other number, which is what makes the reset easy to miss during a quick glance.

What refillIfEmpty in 08 quietly prevents, and where 06 actually handles it

08's refillIfEmpty calls addRow from a fixed STOCK array the instant fewer than two rows remain, so this demo's cart can never actually reach a true empty state no matter how many times a visitor removes a row. 06 is the pattern built to handle that moment for real — its crossfade only runs once the item count value actually reaches zero, which is exactly the state 08 is designed never to produce.

Three variants and accessibility

Treat the numbers below as a starting point once the demo items have been swapped for a real product feed — the computed value stays the same, only the constant changes.

Variant What changes What it trades off
Spring damping ratio Item 01's ZETA constant from 0.42 to 0.22 At 0.42 the panel overshoots once and settles quickly; at 0.22 the underdamped term stays dominant longer, so the panel visibly swings past its target two or three more times before the position value finally holds still
Rubber-band resistance threshold Item 05's THRESHOLD constant from 90px to 150px At 90px resistance begins almost as soon as a drag starts, leaving little room to feel the curve before the dismiss check fires; at 150px the resistance zone is longer, so a visitor feels the pull building and the snap-back on release before the card would ever leave the drawer
Remove-item collapse duration Item 08's DUR_MS constant from 320ms to 620ms At 320ms a removed row collapses fast enough that the rows below appear to jump up instantly; at 620ms the same shrink plays slowly enough to watch the gap close, at the cost of the drawer feeling less snappy right after a click

This zip ships the 0.42, 90px, and 320ms values.

Why prefers-reduced-motion still leaves every computed value reachable by hand

All nine check prefers-reduced-motion in both JS and CSS before starting their own autoplay preview loop, so a reduced-motion visitor who clicks, drags, or scrolls by hand still reaches the same recomputed position, distance, or count value — only the demo's self-playing loop is what stops. Decorative glyphs are marked aria-hidden="true" rather than announced on their own: 01's close icon, 05's trash icon, 06's empty-cart icon, and 09's cart icon under the badge number all fall into this group, leaving each real control's own aria-label — "Close," "Remove," "Decrease quantity," "Increase quantity," and "Add" — as the only text a screen reader reads for that button.

FAQ

Should a cart drawer design start with the panel's open animation or the empty-state message?

Start with whichever value a visitor sees most often — for most carts that's 01's open-position value, since a visitor opens the drawer far more times than they ever see it empty, while 06's crossfade only matters the first time a cart with zero items in it gets its first row.

Do any of these nine patterns touch a real checkout or payment backend?

No — every quantity change, removal, and the checkout bar's own scroll reveal in 07 stays a local state transition, nothing here calls fetch or a payment API, and every product name and price in the set is invented rather than pulled from a real catalog.

Is this a cart drawer ui design example only, or code meant to ship?

It's meant to be used directly rather than kept as a demo alone — each of the nine is 25 lines or fewer of the core computation shown above, none of the nine reaches outside itself for a library, and the fixed local arrays are the only part meant to be replaced with a real product feed.

Sources: MDN — easing-function · MDN — Pointer events · MDN — Window.requestAnimationFrame · MDN — ARIA dialog role · MDN — prefers-reduced-motion

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