/* =====================================================================
   Sam奧數遊戲 - Base reset + typography + background canvas
   ===================================================================== */

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

html {
    -webkit-text-size-adjust: 100%;
    text-rendering: optimizeLegibility;
    -webkit-font-smoothing: antialiased;
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-body);
    color: var(--c-text-1);
    background: var(--c-bg-0);
    line-height: var(--lh-normal);
    min-height: 100vh;
    overflow-x: hidden;
    position: relative;
}

/* Animated space background: gradient + grid + scanline + stars */
body::before {
    content: "";
    position: fixed;
    inset: 0;
    background: var(--grad-hero);
    z-index: -3;
}

body::after {
    content: "";
    position: fixed;
    inset: 0;
    background-image:
        linear-gradient(rgba(0, 240, 255, 0.04) 1px, transparent 1px),
        linear-gradient(90deg, rgba(0, 240, 255, 0.04) 1px, transparent 1px);
    background-size: 48px 48px;
    z-index: -2;
    mask-image: radial-gradient(ellipse at center, black 0%, transparent 75%);
    -webkit-mask-image: radial-gradient(ellipse at center, black 0%, transparent 75%);
    animation: grid-pan 30s linear infinite;
}

@keyframes grid-pan {
    from { background-position: 0 0, 0 0; }
    to   { background-position: 48px 48px, 48px 48px; }
}

/* Scanline overlay */
.scanlines::before {
    content: "";
    position: fixed;
    inset: 0;
    background: repeating-linear-gradient(
        0deg,
        rgba(255,255,255,0.015) 0px,
        rgba(255,255,255,0.015) 1px,
        transparent 1px,
        transparent 3px
    );
    pointer-events: none;
    z-index: 1000;
}

a { color: var(--c-neon-cyan); text-decoration: none; }
a:hover { color: var(--c-neon-magenta); }

img, svg { max-width: 100%; display: block; }

button, input, select, textarea {
    font: inherit;
    color: inherit;
}

h1, h2, h3, h4 {
    font-family: var(--font-display);
    font-weight: var(--fw-bold);
    line-height: var(--lh-tight);
    color: var(--c-text-0);
    letter-spacing: 0.02em;
}

h1 { font-size: var(--fs-3xl); }
h2 { font-size: var(--fs-2xl); }
h3 { font-size: var(--fs-xl); }
h4 { font-size: var(--fs-lg); }

p { color: var(--c-text-2); }

::selection {
    background: var(--c-neon-cyan);
    color: var(--c-text-on-neon);
}

/* Container helpers */
.container {
    width: 100%;
    max-width: var(--container-max);
    margin-inline: auto;
    padding-inline: var(--sp-4);
}

.container-narrow {
    width: 100%;
    max-width: var(--container-narrow);
    margin-inline: auto;
    padding-inline: var(--sp-4);
}

/* Utility */
.text-gradient {
    background: var(--grad-neon);
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
}

.text-gradient-gold {
    background: var(--grad-gold);
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
}

.glass {
    background: var(--c-bg-glass);
    backdrop-filter: blur(18px) saturate(150%);
    -webkit-backdrop-filter: blur(18px) saturate(150%);
    border: 1px solid rgba(255,255,255,0.08);
    box-shadow: var(--shadow-card);
}

.hidden { display: none !important; }
.sr-only {
    position: absolute;
    width: 1px; height: 1px;
    padding: 0; margin: -1px;
    overflow: hidden; clip: rect(0,0,0,0);
    white-space: nowrap; border: 0;
}

/* Loading spinner */
.spinner {
    width: 24px; height: 24px;
    border: 3px solid rgba(0,240,255,0.2);
    border-top-color: var(--c-neon-cyan);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* Scrollbar */
::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: var(--c-bg-1); }
::-webkit-scrollbar-thumb {
    background: linear-gradient(var(--c-neon-cyan), var(--c-neon-magenta));
    border-radius: 8px;
}