/* ── Color palette ── */
:root {
    --color-red: #e74c3c;
    --color-blue: #3498db;
    --color-green: #2ecc71;
    --color-yellow: #f1c40f;
    --color-orange: #e67e22;
    --color-purple: #9b59b6;
    --color-pink: #e91e8c;
    --color-teal: #1abc9c;
    --color-brown: #795548;
    --color-gray: #95a5a6;

    --tube-width: 56px;
    --layer-height: 48px;
    --tube-radius: 0 0 28px 28px;
    --gap: 16px;
    --bg: #1a1a2e;
    --tube-bg: rgba(255, 255, 255, 0.07);
    --tube-border: rgba(255, 255, 255, 0.18);
    --selection-glow: 0 0 0 3px #f1c40f, 0 0 12px #f1c40faa;
    --focus-glow: 0 0 0 3px #3498db, 0 0 12px #3498dbaa;
    --anim-pour: 320ms ease-in-out;
}

/* ── Reset & base ── */
*,
*::before,
*::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    background: var(--bg);
    color: #eee;
    font-family: system-ui, sans-serif;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
}

#app {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 24px;
    padding: 24px;
}

.title {
    font-size: 1.8rem;
    font-weight: 700;
    letter-spacing: 0.05em;
    opacity: 0.9;
}

/* ── Game area ── */
#game {
    display: flex;
    flex-wrap: wrap;
    gap: var(--gap);
    justify-content: center;
    align-items: flex-end;
}

/* ── Tube ── */
.tube {
    display: flex;
    flex-direction: column-reverse; /* layers stack bottom-up */
    width: var(--tube-width);
    border: 2px solid var(--tube-border);
    border-top: none;
    border-radius: var(--tube-radius);
    background: var(--tube-bg);
    cursor: pointer;
    position: relative;
    transition:
        transform 150ms ease,
        box-shadow 150ms ease;
    outline: none;
    user-select: none;
}

.tube:hover {
    transform: translateY(-4px);
}

.tube.selected {
    box-shadow: var(--selection-glow);
    transform: translateY(-8px);
}

.tube.focused {
    box-shadow: var(--focus-glow);
}

.tube.dragging {
    transform: translateY(-12px) scale(1.04);
    opacity: 0.85;
}

/* ── Liquid layer ── */
.layer {
    width: 100%;
    height: var(--layer-height);
    transition:
        height var(--anim-pour),
        opacity var(--anim-pour);
    border-radius: 0;
}

/* first (bottom) layer gets rounded bottom */
.layer:first-child {
    border-radius: 0 0 26px 26px;
}

/* ── Color assignments ── */
.layer[data-color="red"] {
    background: var(--color-red);
}
.layer[data-color="blue"] {
    background: var(--color-blue);
}
.layer[data-color="green"] {
    background: var(--color-green);
}
.layer[data-color="yellow"] {
    background: var(--color-yellow);
}
.layer[data-color="orange"] {
    background: var(--color-orange);
}
.layer[data-color="purple"] {
    background: var(--color-purple);
}
.layer[data-color="pink"] {
    background: var(--color-pink);
}
.layer[data-color="teal"] {
    background: var(--color-teal);
}
.layer[data-color="brown"] {
    background: var(--color-brown);
}
.layer[data-color="gray"] {
    background: var(--color-gray);
}

/* empty placeholder slot */
.layer.empty {
    background: transparent;
    height: var(--layer-height);
}

/* ── Layer enter/exit animations ── */
@keyframes layer-in {
    from {
        transform: scaleY(0);
        opacity: 0;
    }
    to {
        transform: scaleY(1);
        opacity: 1;
    }
}

@keyframes layer-out {
    from {
        transform: scaleY(1);
        opacity: 1;
    }
    to {
        transform: scaleY(0);
        opacity: 0;
    }
}

.layer.entering {
    animation: layer-in var(--anim-pour) ease-out forwards;
    transform-origin: bottom;
}
.layer.exiting {
    animation: layer-out var(--anim-pour) ease-in forwards;
    transform-origin: top;
}

/* ── Controls ── */
.controls {
    display: flex;
    gap: 12px;
}

.controls button {
    background: rgba(255, 255, 255, 0.1);
    border: 1px solid rgba(255, 255, 255, 0.2);
    color: #eee;
    padding: 8px 20px;
    border-radius: 8px;
    font-size: 1rem;
    cursor: pointer;
    transition: background 150ms;
}

.controls button:hover {
    background: rgba(255, 255, 255, 0.2);
}
.controls button:active {
    background: rgba(255, 255, 255, 0.3);
}

@keyframes shake {
    0%,
    100% {
        transform: translateX(0);
    }
    20% {
        transform: translateX(-6px);
    }
    40% {
        transform: translateX(6px);
    }
    60% {
        transform: translateX(-4px);
    }
    80% {
        transform: translateX(4px);
    }
}

/* ── Win overlay ── */
.win-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.6);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 100;
    backdrop-filter: blur(4px);
}

.win-overlay.hidden {
    display: none;
}

.win-box {
    background: #16213e;
    border: 1px solid rgba(255, 255, 255, 0.15);
    border-radius: 20px;
    padding: 40px 60px;
    text-align: center;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 12px;
    animation: pop-in 300ms cubic-bezier(0.34, 1.56, 0.64, 1);
}

@keyframes pop-in {
    from {
        transform: scale(0.7);
        opacity: 0;
    }
    to {
        transform: scale(1);
        opacity: 1;
    }
}

.win-emoji {
    font-size: 3rem;
}
.win-text {
    font-size: 2rem;
    font-weight: 700;
}
.win-moves {
    font-size: 1rem;
    opacity: 0.7;
}

.win-box button {
    margin-top: 8px;
    background: #3498db;
    border: none;
    color: #fff;
    padding: 10px 32px;
    border-radius: 10px;
    font-size: 1rem;
    cursor: pointer;
    transition: background 150ms;
}

.win-box button:hover {
    background: #2980b9;
}