:root {
            --bg: #0f172a;
            --card: #111827;
            --text: #e5e7eb;
            --accent: #22c55e;
            --accent-2: #38bdf8;
        }
        * { box-sizing: border-box; }
        html, body { height: 100%; }
        html { -webkit-text-size-adjust: 100%; }
        body {
            margin: 0;
            font-family: system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Apple Color Emoji", "Segoe UI Emoji";
            background: radial-gradient(1200px 600px at 10% -10%, rgba(56,189,248,0.15), transparent 65%),
                                    radial-gradient(900px 500px at 120% 20%, rgba(34,197,94,0.15), transparent 60%),
                                    var(--bg);
            color: var(--text);
            display: grid;
            grid-template-rows: auto 1fr auto;
            min-height: 100%;
        }
        header, footer {
            padding: calc(1rem + env(safe-area-inset-top)) calc(1.25rem + env(safe-area-inset-right)) 1rem calc(1.25rem + env(safe-area-inset-left));
            display: flex;
            align-items: center;
            justify-content: space-between;
        }
        header h1 {
            margin: 0;
            font-size: 1.1rem;
            font-weight: 600;
            letter-spacing: 0.4px;
        }
        main {
            display: grid;
            place-items: center;
            padding: 1.5rem;
            padding-left: calc(1.5rem + env(safe-area-inset-left));
            padding-right: calc(1.5rem + env(safe-area-inset-right));
        }
        .grid {
            width: min(900px, 92vw);
            display: grid;
            grid-template-columns: 1fr; /* mobile-first */
            gap: 1rem;
        }
        @media (min-width: 560px) {
            .grid { grid-template-columns: repeat(2, minmax(220px, 1fr)); }
        }

        .btn {
            appearance: none;
            border: 1px solid rgba(229,231,235,0.12);
            background: linear-gradient(180deg, rgba(255,255,255,0.04), rgba(255,255,255,0.01));
            color: var(--text);
            padding: 1.25rem 1.1rem;
            border-radius: 14px;
            text-align: left;
            cursor: pointer;
            transition: transform 120ms ease, border-color 120ms ease, background 120ms ease, box-shadow 120ms ease;
            position: relative;
            overflow: hidden;
            min-height: 64px;            /* bigger touch target */
            display: block;              /* anchors fill grid cell */
            text-decoration: none;       /* remove link underline */
            -webkit-tap-highlight-color: transparent;
            touch-action: manipulation;
        }
        .btn strong { display: block; font-size: 1.2rem; margin-bottom: 0.35rem; }
        .btn span { opacity: 0.8; font-size: 0.95rem; }

        @media (hover: hover) {
            .btn:hover { transform: translateY(-2px); border-color: rgba(229,231,235,0.24); }
        }
        .btn:active { transform: translateY(0); }
        .btn:focus-visible {
            outline: 0;
            box-shadow: 0 0 0 3px rgba(56,189,248,0.45);
        }

        .btn:nth-child(1)::after,
        .btn:nth-child(2)::after,
        .btn:nth-child(3)::after,
        .btn:nth-child(4)::after {
            content: "";
            position: absolute;
            inset: 0;
            opacity: 0;
            transition: opacity 180ms ease;
            pointer-events: none;
        }
        .btn:nth-child(1)::after { background: radial-gradient(600px 200px at 0% 0%, rgba(56,189,248,0.12), transparent 60%); }
        .btn:nth-child(2)::after { background: radial-gradient(600px 200px at 100% 0%, rgba(34,197,94,0.12), transparent 60%); }
        .btn:nth-child(3)::after { background: radial-gradient(600px 200px at 0% 100%, rgba(250,204,21,0.12), transparent 60%); }
        .btn:nth-child(4)::after { background: radial-gradient(600px 200px at 100% 100%, rgba(244,114,182,0.12), transparent 60%); }
        @media (hover: hover) {
            .btn:hover::after { opacity: 1; }
        }

        .sr-only {
            position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden;
            clip: rect(0,0,1px,1px); white-space: nowrap; border: 0;
        }