/* ========================================
   SUDOKU REBELS — MAIN STYLES (LIGHT)
   ======================================== */

:root {
    --primary:        #5b8dee;
    --primary-dark:   #3d74d9;
    --primary-light:  #93c5fd;
    --accent:         #f59e0b;
    --accent-dark:    #d97706;
    --accent-light:   #fcd34d;
    --success:        #059669;
    --danger:         #dc2626;
    --warning:        #f59e0b;
    --info:           #0284c7;
    --bg:             #ffffff;
    --bg-soft:        #f8fafc;
    --bg-mid:         #f1f5f9;
    --text:           #0f172a;
    --text-mid:       #334155;
    --text-muted:     #64748b;
    --border:         #e2e8f0;
    --white:          #ffffff;

    --grad-hero:    linear-gradient(135deg, #f0f7ff 0%, #dbeafe 50%, #e8f0fd 100%);
    --grad-primary: linear-gradient(135deg, #5b8dee 0%, #93c5fd 100%);
    --grad-accent:  linear-gradient(135deg, #f59e0b 0%, #fbbf24 100%);

    --font-base:  'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    --radius:     0.375rem;
    --radius-lg:  0.75rem;
    --radius-xl:  1rem;
    --shadow-sm:  0 1px 3px rgba(0,0,0,.08);
    --shadow:     0 4px 12px rgba(0,0,0,.1);
    --shadow-lg:  0 8px 30px rgba(0,0,0,.12);
    --shadow-acc: 0 4px 14px rgba(245,158,11,.35);
    --shadow-pri: 0 4px 14px rgba(91,141,238,.3);
    --trans:      all .3s ease-in-out;
    --trans-fast: all .15s ease-in-out;
}

/* ── RESET ──────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 72px; }

body {
    font-family: var(--font-base);
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
    overflow-x: hidden;
}

a { color: var(--primary); text-decoration: none; transition: var(--trans-fast); }
a:hover { color: var(--primary-light); }

/* ── NAVBAR ─────────────────────────────── */
.navbar {
    background: rgba(255,255,255,.96) !important;
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border);
    padding: .75rem 0;
    box-shadow: var(--shadow-sm);
}

.navbar-brand {
    font-size: 1.4rem;
    font-weight: 800;
    color: var(--primary) !important;
    letter-spacing: -.5px;
}
.navbar-brand span { color: var(--accent); }
.navbar-brand:hover { display: inline-block; transform: scale(1.04); }

.navbar-toggler { border-color: var(--border); }
.navbar-toggler:focus { box-shadow: none; }

.navbar .btn-outline-primary {
    border-color: var(--primary);
    color: var(--primary);
    font-weight: 600;
    border-radius: var(--radius-lg);
    transition: var(--trans);
}
.navbar .btn-outline-primary:hover {
    background: var(--primary);
    color: var(--white);
    box-shadow: var(--shadow-pri);
}
.navbar .btn-accent {
    background: var(--grad-accent);
    color: var(--white) !important;
    font-weight: 700;
    border: none;
    border-radius: var(--radius-lg);
    transition: var(--trans);
}
.navbar .btn-accent:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-acc);
}

/* ── HERO ───────────────────────────────── */
.hero-section {
    background: var(--grad-hero);
    min-height: 100vh;
    display: flex;
    align-items: center;
    padding-top: 72px;
    position: relative;
    overflow: hidden;
}
.hero-section::before {
    content: '';
    position: absolute;
    inset: 0;
    background:
        radial-gradient(circle at 15% 50%, rgba(30,58,138,.06) 0%, transparent 55%),
        radial-gradient(circle at 85% 20%, rgba(245,158,11,.07) 0%, transparent 50%);
    pointer-events: none;
}

.hero-content { position: relative; z-index: 2; }

.hero-badge {
    display: inline-block;
    background: rgba(30,58,138,.08);
    color: var(--primary);
    border: 1px solid rgba(30,58,138,.15);
    border-radius: 999px;
    padding: .35rem 1rem;
    font-size: .85rem;
    font-weight: 600;
    margin-bottom: 1.25rem;
}

.hero-title {
    font-size: clamp(2.2rem, 5vw, 4rem);
    font-weight: 900;
    color: var(--text);
    line-height: 1.1;
    margin-bottom: 1.25rem;
    letter-spacing: -1px;
}
.hero-title .highlight { color: var(--primary); }

.hero-subtitle {
    font-size: 1.1rem;
    color: var(--text-mid);
    max-width: 520px;
    margin-bottom: 2rem;
}

.hero-buttons { display: flex; flex-wrap: wrap; gap: 1rem; }
.hero-buttons .btn {
    padding: .8rem 2rem;
    font-size: 1rem;
    font-weight: 700;
    border-radius: var(--radius-xl);
    transition: var(--trans);
}
.hero-buttons .btn:hover { transform: translateY(-3px); }

.btn-hero-primary {
    background: var(--grad-primary);
    color: var(--white) !important;
    border: none;
    box-shadow: var(--shadow-pri);
}
.btn-hero-primary:hover { box-shadow: 0 8px 24px rgba(30,58,138,.35); }

.btn-hero-secondary {
    background: var(--white);
    border: 2px solid var(--border);
    color: var(--text) !important;
    box-shadow: var(--shadow-sm);
}
.btn-hero-secondary:hover { border-color: var(--primary); box-shadow: var(--shadow); }

.hero-stats {
    display: flex;
    gap: 1.5rem;
    margin-top: 1.75rem;
    flex-wrap: wrap;
}
.hero-stat {
    font-size: .88rem;
    color: var(--text-muted);
    display: flex;
    align-items: center;
    gap: .35rem;
}
.hero-stat i { color: var(--accent); }

.hero-logo-img {
    width: min(360px, 82vw);
    border-radius: 2rem;
    box-shadow:
        0 32px 80px rgba(0,0,0,.22),
        0 8px 24px rgba(30,58,138,.18),
        0 0 0 1px rgba(255,255,255,.08);
    transition: transform .35s ease, box-shadow .35s ease;
    animation: heroFloat 4s ease-in-out infinite;
}
.hero-logo-img:hover {
    transform: scale(1.04) translateY(-6px);
    box-shadow:
        0 40px 100px rgba(0,0,0,.28),
        0 12px 32px rgba(30,58,138,.22);
}

@keyframes heroFloat {
    0%, 100% { transform: translateY(0); }
    50%       { transform: translateY(-10px); }
}

/* Sudoku grid decorativo */
.sudoku-grid-demo {
    display: grid;
    grid-template-columns: repeat(9, 1fr);
    gap: 2px;
    max-width: 360px;
    margin: 0 auto;
    padding: 14px;
    background: var(--white);
    border-radius: var(--radius-xl);
    border: 1px solid var(--border);
    box-shadow: var(--shadow-lg);
    animation: float 6s ease-in-out infinite;
}
.sudoku-cell {
    aspect-ratio: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: .82rem;
    font-weight: 600;
    border-radius: 3px;
    background: var(--bg-soft);
    color: var(--text-muted);
    border: 1px solid var(--border);
    transition: var(--trans-fast);
}
.sudoku-cell.given {
    color: var(--primary);
    background: rgba(30,58,138,.07);
    border-color: rgba(30,58,138,.15);
    font-weight: 800;
}
.sudoku-cell.box-border-r { border-right: 2px solid #94a3b8; }
.sudoku-cell.box-border-b { border-bottom: 2px solid #94a3b8; }

@keyframes float {
    0%, 100% { transform: translateY(0); }
    50%       { transform: translateY(-14px); }
}
@keyframes fadeInUp {
    0%   { opacity: 0; transform: translateY(20px); }
    100% { opacity: 1; transform: translateY(0); }
}

/* ── FEATURES ───────────────────────────── */
.features-section {
    padding: 5rem 0;
    background: var(--bg-soft);
    border-top: 1px solid var(--border);
}

.section-title {
    font-size: 2rem;
    font-weight: 800;
    color: var(--text);
    margin-bottom: .5rem;
}
.section-title span { color: var(--primary); }
.section-subtitle { color: var(--text-muted); font-size: 1.05rem; }

.feature-card {
    background: var(--white);
    border: 1px solid var(--border);
    border-radius: var(--radius-xl);
    padding: 2rem 1.5rem;
    text-align: center;
    height: 100%;
    transition: var(--trans);
    position: relative;
    overflow: hidden;
    box-shadow: var(--shadow-sm);
}
.feature-card::before {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0;
    height: 3px;
    background: var(--grad-primary);
    transform: scaleX(0);
    transition: var(--trans);
}
.feature-card:hover {
    transform: translateY(-8px);
    border-color: rgba(30,58,138,.2);
    box-shadow: var(--shadow-lg);
}
.feature-card:hover::before { transform: scaleX(1); }

.feature-icon {
    width: 68px;
    height: 68px;
    border-radius: 50%;
    background: rgba(30,58,138,.07);
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 1.25rem;
    transition: var(--trans);
}
.feature-card:hover .feature-icon { background: var(--grad-primary); }
.feature-icon i { font-size: 1.65rem; color: var(--primary); transition: var(--trans); }
.feature-card:hover .feature-icon i { color: var(--white); }

.feature-card h4 { color: var(--text); font-weight: 700; margin-bottom: .4rem; }
.feature-card p  { color: var(--text-muted); margin: 0; font-size: .94rem; }

/* ── GAME MODES ─────────────────────────── */
.modes-section {
    padding: 5rem 0;
    background: var(--bg);
    border-top: 1px solid var(--border);
}

.mode-card {
    background: var(--white);
    border: 2px solid var(--border);
    border-radius: var(--radius-xl);
    padding: 2rem 1.5rem;
    text-align: center;
    transition: var(--trans);
    box-shadow: var(--shadow-sm);
}
.mode-card:hover {
    border-color: var(--primary);
    box-shadow: var(--shadow-lg), 0 0 0 1px var(--primary);
    transform: translateY(-5px);
}
.mode-size {
    font-size: 2.6rem;
    font-weight: 900;
    color: var(--primary);
    line-height: 1;
    margin-bottom: .4rem;
}
.mode-name { font-weight: 700; color: var(--text); margin-bottom: .4rem; }
.mode-desc { color: var(--text-muted); font-size: .9rem; margin: 0; }
.mode-badge {
    display: inline-block;
    padding: .25rem .8rem;
    border-radius: 999px;
    font-size: .75rem;
    font-weight: 700;
    margin-top: .75rem;
}
.badge-easy   { background: #dcfce7; color: #15803d; }
.badge-medium { background: #fef9c3; color: #a16207; }
.badge-hard   { background: #fee2e2; color: #b91c1c; }

/* ── CTA ────────────────────────────────── */
.cta-section {
    padding: 5rem 0;
    background: var(--grad-primary);
    text-align: center;
    position: relative;
    overflow: hidden;
}
.cta-section::before {
    content: '';
    position: absolute;
    inset: 0;
    background: radial-gradient(circle at 50% 50%, rgba(255,255,255,.06) 0%, transparent 70%);
}
.cta-section h2 { font-size: 2.4rem; font-weight: 900; position: relative; z-index: 1; color: var(--white); }
.cta-section p  { color: rgba(255,255,255,.8); font-size: 1.1rem; position: relative; z-index: 1; }
.cta-section .btn-white {
    background: var(--white);
    color: var(--primary) !important;
    font-weight: 700;
    border: none;
    border-radius: var(--radius-xl);
    padding: .85rem 2.5rem;
    font-size: 1.05rem;
    transition: var(--trans);
    box-shadow: var(--shadow);
}
.cta-section .btn-white:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-lg);
}

/* ── FOOTER ─────────────────────────────── */
footer {
    background: var(--bg-soft);
    border-top: 1px solid var(--border);
    padding: 2rem 0;
    color: var(--text-muted);
    font-size: .88rem;
    text-align: center;
}
footer a { color: var(--primary); }

/* ── MODALS ─────────────────────────────── */
.modal-content {
    background: var(--white);
    border: 1px solid var(--border);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-lg);
    color: var(--text);
}
.modal-header {
    background: var(--grad-primary);
    border: none;
    padding: 1.2rem 1.5rem;
    border-radius: var(--radius-xl) var(--radius-xl) 0 0;
}
.modal-title { font-weight: 700; color: var(--white); }
.modal-header .btn-close { filter: invert(1); opacity: .75; }
.modal-header .btn-close:hover { opacity: 1; }
.modal-body { padding: 1.75rem; }

.modal .form-label { color: var(--text-mid); font-weight: 600; margin-bottom: .35rem; font-size: .9rem; }
.modal .form-control {
    background: var(--bg-soft);
    border: 1.5px solid var(--border);
    border-radius: var(--radius-lg);
    color: var(--text);
    padding: .6rem 1rem;
    transition: var(--trans-fast);
}
.modal .form-control::placeholder { color: var(--text-muted); }
.modal .form-control:focus {
    background: var(--white);
    border-color: var(--primary);
    color: var(--text);
    box-shadow: 0 0 0 3px rgba(30,58,138,.12);
}
.modal .form-control.is-valid   { border-color: var(--success); }
.modal .form-control.is-invalid { border-color: var(--danger); }

.modal .input-group .btn-outline-secondary {
    background: var(--bg-soft);
    border: 1.5px solid var(--border);
    border-left: none;
    color: var(--text-muted);
}
.modal .input-group .btn-outline-secondary:hover { color: var(--text); background: var(--bg-mid); }

.modal .btn-primary {
    background: var(--grad-primary);
    color: var(--white) !important;
    border: none;
    font-weight: 700;
    padding: .7rem;
    border-radius: var(--radius-lg);
    transition: var(--trans);
    box-shadow: var(--shadow-pri);
}
.modal .btn-primary:hover { transform: translateY(-2px); box-shadow: 0 6px 20px rgba(30,58,138,.3); }

.modal .btn-outline-secondary {
    color: var(--text-muted);
    border-color: var(--border);
}
.modal .btn-outline-secondary:hover { background: var(--bg-mid); color: var(--text); }

.modal a { color: var(--primary); font-weight: 600; }
.modal a:hover { color: var(--primary-light); }

.modal .form-text { color: var(--text-muted); font-size: .82rem; }
.modal .text-danger  { color: var(--danger)  !important; }
.modal .text-success { color: var(--success) !important; }

/* Loading button */
.btn.loading { color: transparent !important; pointer-events: none; position: relative; }
.btn.loading::after {
    content: '';
    position: absolute;
    top: 50%; left: 50%;
    transform: translate(-50%,-50%);
    width: 18px; height: 18px;
    border: 2px solid rgba(30,58,138,.3);
    border-top-color: var(--primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}
@keyframes spin { to { transform: translate(-50%,-50%) rotate(360deg); } }

/* ── RESPONSIVE ─────────────────────────── */
@media (max-width: 991px) {
    .hero-section { text-align: center; }
    .hero-subtitle { margin: 0 auto 2rem; }
    .hero-buttons { justify-content: center; }
    .hero-stats   { justify-content: center; }
    .sudoku-grid-demo { margin-top: 2.5rem; }
}
@media (max-width: 767px) {
    .hero-title { font-size: 2.2rem; }
    .hero-buttons { flex-direction: column; align-items: center; }
    .hero-buttons .btn { width: 100%; max-width: 280px; }
    .modal-body { padding: 1.25rem; }
    .section-title { font-size: 1.65rem; }
}