js-dev-onboarding-24-play/src/css/ui.scss

@use "sass:math";

#ui {
  flex-grow: 1;
}

/* ============================================================
   HUD — screen-space overlay built by HudC.

   Structure follows BEM: each visual block (invasion bar, resources,
   weapon, tutorial hint, death end-card) is a `.hud-<block>` class with
   `&__element` children and `&--modifier` states. SCSS nesting (`&`) keeps
   each block's rules in one place so we never repeat the prefix.

   The whole HUD is viewport-relative: lengths use vw via the fluid helpers
   below, so it scales as one piece with the device.
   ============================================================ */

// Core fluid helper: a clamp() that grows linearly with the viewport from $min
// (at $vp-min) to $max (at $vp-max), and stays flat outside that range.
//
// The unit it scales against is the CSS variable --fluid-unit, set on #hud:
// 1vw in portrait (scale with width) and 1vh in landscape (scale with the
// limiting height). Landscape screens are wide but short, so scaling by width
// there blows the HUD up — height keeps it proportional.
@function fluid-clamp($min, $max, $vp-min: 320px, $vp-max: 900px) {
  $slope: math.div($max - $min, $vp-max - $vp-min); // px/px → unitless
  $intercept: $min - $slope * $vp-min; // px
  @return clamp(#{$min}, #{$intercept} + #{$slope * 100} * var(--fluid-unit, 1vw), #{$max});
}

// Fluid font-size from a px range.
@mixin fluid($min, $max) {
  font-size: fluid-clamp($min, $max);
}

// Fluid image size from px ranges. Pass 2 args for a square image (height reuses
// the width range) or 4 args for a non-square one (separate height range).
@mixin fluid-img($wmin, $wmax, $hmin: null, $hmax: null) {
  width: fluid-clamp($wmin, $wmax);
  @if $hmin == null {
    height: fluid-clamp($wmin, $wmax); // square: reuse the width range
  } @else if $hmax == null {
    height: fluid-clamp($hmin, $wmax); // only a min height given: cap at the width max
  } @else {
    height: fluid-clamp($hmin, $hmax); // full height range given
  }
}

// Fluid value for any single property from a px range — bounds it between
// $min/$max while it scales with the viewport (e.g. to cap the invasion bar).
@mixin fluid-prop($prop, $min, $max) {
  #{$prop}: fluid-clamp($min, $max);
}

#hud {
  position: fixed;
  max-width: 1280px;
  margin: 0 auto;
  padding-inline: 16px;
  inset: 0;
  z-index: 9999;
  pointer-events: none;
  font-family: "PassionOne", "Roboto", sans-serif;

  // Portrait: every fluid size scales with viewport width.
  --fluid-unit: 1vw;

  @media screen and (min-width: 500px) {
    padding-inline: 24px;
  }

  // Landscape: scale with height instead (short screens → keep the HUD small).
  @media (orientation: landscape) {
    --fluid-unit: 1vh;
  }
}

/* ---- Zombie Invasion bar (top) ----------------------------
   "HURRY UP" and the countdown share this one container and crossfade: the
   --hurry-phase modifier shows the hurry text and hides the bar; dropping it
   reveals the bar. The zombie head rides the fill's leading edge. */
.hud-invasion {
  position: absolute;
  min-height: 80px;
  padding-inline: 64px;
  top: 0.5rem;
  left: 50%;
  transform: translate(-50%);
  width: 100%;
  max-width: 768px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 0.25rem;
  transition: opacity 0.4s ease;

  @media (orientation: landscape) {
    padding-inline: 80px;
  }

  // Fully hidden (before the onboarding reaches the invasion stage, and after death).
  &--hidden {
    opacity: 0;
  }

  &__title {
    @include fluid(24px, 48px);
    text-align: center;
    color: #fff;
    letter-spacing: 1px;
    -webkit-text-stroke: 1px #000;
    -webkit-text-fill-color: #fff;
  }

  &__row {
    display: flex;
    align-items: center;
  }

  // Holds the track + the head that rides the fill's moving edge.
  &__bar {
    position: relative;
    flex: 1;
    display: flex;
    align-items: center;
  }

  &__track {
    width: 100%;
    @include fluid-prop(height, 20px, 32px); // bound the bar thickness so it can't blow up
    background: linear-gradient(to bottom, rgba(0, 0, 0, 0.7), rgba(0, 0, 0, 0.45));
    border: 2px solid #000;
    border-radius: 1000px;
    overflow: hidden;
  }

  &__fill {
    height: 100%;
    width: 100%;
    // glossy green: highlight on top → base → darker bottom (width set per-frame in JS)
    background: linear-gradient(to bottom, #c2f57a 0%, #7fd23a 45%, #4f9e18 100%);

    // Final stretch (low time left): glossy red.
    &--low {
      background: linear-gradient(to bottom, #ff9a6a 0%, #f0512c 45%, #c5301a 100%);
    }
  }

  // The zombie head sits on the fill's leading edge; `left` is set per-frame in
  // JS (0%..100% of the bar). The transform here only centers it — the shake
  // animation lives on the inner <img>, so the two transforms don't fight.
  &__head-wrap {
    position: absolute;
    top: 50%;
    left: 100%;
    transform: translate(-50%, -50%);
    z-index: 2;
  }

  &__head {
    @include fluid-img(44px, 70px);
    display: block; // kill the inline-image descender gap so it centers on the track
    object-fit: contain;
    filter: drop-shadow(0 0.5vw 0.8vw rgba(0, 0, 0, 0.5));
    flex: none;
    transform-origin: center;

    // Half time left: the icon grows and shakes to draw attention.
    &--alert {
      animation: hud-zombie-shake 0.45s ease-in-out infinite;
    }
    // Red zone: shake harder + bigger. Declared after --alert so it wins when both are set.
    &--alert-strong {
      animation: hud-zombie-shake-strong 0.28s ease-in-out infinite;
    }
  }

  // "HURRY UP" overlays the bar in the same box; absolute + inset:0 centers it
  // over the bar regardless of the container's side padding.
  &__hurry {
    @include fluid(48px, 64px);
    position: absolute;
    inset: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    color: #fff;
    letter-spacing: 1px;
    -webkit-text-stroke: 1px #000;
    opacity: 0;
    transition: opacity 0.35s ease;
    pointer-events: none;
  }

  // Crossfade between the two states (both transition opacity).
  &__title,
  &__row {
    transition: opacity 0.35s ease;
  }
  &--hurry-phase &__hurry {
    opacity: 1;
  }
  &--hurry-phase &__title,
  &--hurry-phase &__row {
    opacity: 0;
  }
}

/* ---- Resources (top-right) -------------------------------- */
.hud-resources {
  position: absolute;
  top: 20%;
  right: 16px;
  display: flex;
  flex-direction: column;
  gap: 0.1rem;
  align-items: flex-end;

  @media screen and (min-width: 500px) {
    right: 24px;
  }

  @media (orientation: landscape) {
    top: 30%;
  }

  // One resource panel. The background art already includes the icon, so the
  // whole panel is both the loot fly-target and the thing that pulses on collect.
  &__panel {
    @include fluid-img(64px, 96px, 30px, 46px);
    position: relative;
    background-size: 100% 100%;
    background-repeat: no-repeat;
    transition: transform 0.12s ease-out;
  }

  &__count {
    @include fluid(13px, 22px);
    position: absolute;
    left: 6%;
    right: 28%; // keep the number clear of the colored tab on the right
    top: 0;
    bottom: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #fff;
    font-family: Roboto, sans-serif;
    font-weight: 600;
  }
}

/* ---- Weapon panel (bottom-left) --------------------------- */
.hud-weapon {
  @include fluid-img(64px, 80px);
  position: absolute;
  bottom: 25%;
  background-size: 100% 100%;
  background-repeat: no-repeat;
  display: flex;
  align-items: center;
  justify-content: center;

  &__icon {
    width: 70%;
    height: 70%;
    position: relative;
    top: -5px;
    object-fit: contain;
  }

  &__lvl {
    @include fluid(14px, 18px);
    font-family: Roboto, sans-serif;
    font-weight: 600;
    position: absolute;
    bottom: 1%;
    left: 62%;
    transform: translateX(-50%);
    color: #fff;
    letter-spacing: 1px;
    white-space: nowrap;
  }
}

/* ---- Onboarding hint -------------------------------------- */
/* Centered hint ("DRAG TO MOVE") that fades + scales in/out. */
.hud-tutorial {
  @include fluid(30px, 56px);
  position: absolute;
  top: 63%;
  left: 50%;
  transform: translate(-50%, -50%) scale(0.9);
  text-align: center;
  color: #fff;
  letter-spacing: 1px;
  -webkit-text-stroke: 1px #000;
  opacity: 0;
  transition:
    opacity 0.25s ease,
    transform 0.25s ease;
  white-space: nowrap;

  &--show {
    opacity: 1;
    transform: translate(-50%, -50%) scale(1);
  }
}

/* ---- Death end-card --------------------------------------- */
/* The zombie icon flies to center (smooth ease-out + fade), then the button. */
.hud-endcard {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.3rem;

  &__zombie {
    @include fluid-img(150px, 300px);
    object-fit: contain;
    filter: drop-shadow(0 1vw 2vw rgba(0, 0, 0, 0.6));
    opacity: 0;
    transition:
      transform 1s cubic-bezier(0.16, 1, 0.3, 1),
      opacity 0.6s ease;
    will-change: transform, opacity;
  }

  // Revealed once the death animation has played (set in JS).
  &--show .hud-endcard__zombie {
    opacity: 1;
  }
}

@keyframes hud-zombie-shake {
  0%,
  100% {
    transform: scale(1.25) rotate(0deg);
  }
  25% {
    transform: scale(1.25) rotate(-12deg);
  }
  75% {
    transform: scale(1.25) rotate(12deg);
  }
}
@keyframes hud-zombie-shake-strong {
  0%,
  100% {
    transform: scale(1.45) rotate(0deg);
  }
  25% {
    transform: scale(1.45) rotate(-22deg);
  }
  75% {
    transform: scale(1.45) rotate(22deg);
  }
}