* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html, body {
    width: 100%;
    height: 100%;
    overflow: hidden;
    background: #0a0a12;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    color: #e0e0e0;
}

/* ─── Layout ─── */
#app {
    display: flex;
    width: 100%;
    height: 100%;
}

/* ─── Side panel ─── */
#panel {
    width: 300px;
    min-width: 300px;
    height: 100%;
    background: #12121e;
    border-right: 2px solid #ff4500;
    overflow-y: auto;
    overflow-x: hidden;
    transition: min-width 0.3s ease, width 0.3s ease, opacity 0.3s ease;
    z-index: 10;
    display: flex;
    flex-direction: column;
}

#panel.collapsed {
    width: 0;
    min-width: 0;
    overflow: hidden;
    opacity: 0;
    border-right: none;
}

#panel-header {
    padding: 14px 16px;
    text-align: center;
    background: linear-gradient(180deg, #1e1a30, #12121e);
    border-bottom: 1px solid rgba(255, 69, 0, 0.25);
    flex-shrink: 0;
}

#panel-header h1 {
    font-size: 17px;
    color: #ff6b35;
    text-shadow: 0 0 12px rgba(255, 107, 53, 0.4);
    letter-spacing: 0.5px;
}

/* GUI container fills available space */
#gui-container {
    flex: 1;
    overflow-y: auto;
    overflow-x: hidden;
}

/* ─── lil-gui overrides ─── */
#gui-container .lil-gui {
    --background-color: #12121e;
    --widget-color: #252540;
    --focus-color: #ff4500;
    --hover-color: #30305a;
    --text-color: #d0d0d0;
    --title-background-color: #1a1a30;
    --title-text-color: #ff8c50;
    --font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    --font-size: 11px;
    --name-width: 48%;
    --slider-knob-width: 3px;
    --slider-input-width: 22%;
    width: 100% !important;
    border: none;
    margin: 0;
}

#gui-container .lil-gui .title {
    border-bottom: 1px solid rgba(255, 69, 0, 0.15);
}

#gui-container .lil-gui.root > .title {
    display: none;
}

/* ─── Explode button footer ─── */
#panel-footer {
    flex-shrink: 0;
    padding: 12px 14px;
    background: #12121e;
    border-top: 1px solid rgba(255, 69, 0, 0.2);
}

#explode-btn {
    display: block;
    width: 100%;
    padding: 14px 10px;
    background: linear-gradient(135deg, #ff3c00, #ff6b35);
    border: 2px solid #ff8c00;
    border-radius: 8px;
    color: #fff;
    font-size: 17px;
    font-weight: 700;
    letter-spacing: 1px;
    cursor: pointer;
    text-shadow: 0 1px 6px rgba(255, 60, 0, 0.7);
    box-shadow: 0 0 18px rgba(255, 69, 0, 0.25),
                inset 0 1px 0 rgba(255, 255, 255, 0.15);
    transition: box-shadow 0.15s ease, transform 0.1s ease;
    user-select: none;
}

#explode-btn:hover {
    box-shadow: 0 0 30px rgba(255, 69, 0, 0.5),
                inset 0 1px 0 rgba(255, 255, 255, 0.2);
}

#explode-btn:active {
    transform: scale(0.97);
    box-shadow: 0 0 12px rgba(255, 69, 0, 0.4);
}

/* ─── Panel toggle button ─── */
#panel-toggle {
    position: fixed;
    top: 10px;
    left: 308px;
    z-index: 100;
    width: 32px;
    height: 32px;
    background: #12121e;
    border: 1px solid #ff4500;
    border-radius: 4px;
    color: #ff6b35;
    font-size: 16px;
    cursor: pointer;
    transition: left 0.3s ease, background 0.15s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    line-height: 1;
    padding: 0;
}

#panel-toggle:hover {
    background: #1e1a30;
}

#panel-toggle.shifted {
    left: 10px;
}

/* ─── Canvas container ─── */
#canvas-container {
    flex: 1;
    height: 100%;
    position: relative;
    overflow: hidden;
}

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

/* ─── WebGL error overlay ─── */
#webgl-error {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: #0a0a12;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    text-align: center;
    padding: 24px;
}

#webgl-error h2 {
    color: #ff4500;
    margin-bottom: 16px;
    font-size: 26px;
}

#webgl-error p {
    color: #999;
    font-size: 15px;
    max-width: 480px;
    line-height: 1.5;
}

/* ─── Scrollbar ─── */
#panel::-webkit-scrollbar,
#gui-container::-webkit-scrollbar {
    width: 5px;
}

#panel::-webkit-scrollbar-track,
#gui-container::-webkit-scrollbar-track {
    background: #12121e;
}

#panel::-webkit-scrollbar-thumb,
#gui-container::-webkit-scrollbar-thumb {
    background: #333;
    border-radius: 3px;
}

#panel::-webkit-scrollbar-thumb:hover,
#gui-container::-webkit-scrollbar-thumb:hover {
    background: #555;
}