/* --------------------------
   THEME COLOR VARIABLES
-------------------------- */
:root {
  --color-bg: #f7fafd;
  --color-hero-gradient: radial-gradient(ellipse at 50% 24%, #10bfff09 0%, transparent 90%);
  --color-nav-bg: #fff;
  --color-nav-border: #eaecef;
  --color-headline: #1675a6;
  --color-accent: #1675a6;
  --color-accent2: #10bfff;
  --color-tagline: #4e5a66;
  --color-muted: #7391a2;
  --color-btn-bg: #1675a6;
  --color-btn-hover: #10bfff;
  --color-btn-text: #fff;
  --color-btn-hover-text: #222;
  --color-logo-glow: #10bfff18;
}
body.light-theme { /* variables already defined for light */ }
body:not(.light-theme) {
  --color-bg: #13191f;
  --color-hero-gradient: radial-gradient(ellipse at 50% 18%, #10bfff2c 0%, transparent 80%);
  --color-nav-bg: rgba(17,18,20,0.97);
  --color-nav-border: #18202a;
  --color-headline: #10bfff;
  --color-accent: #10bfff;
  --color-accent2: #16d9ff;
  --color-tagline: #94a6bb;
  --color-muted: #e9f0fc;
  --color-btn-bg: #10bfff;
  --color-btn-hover: #36d1ff;
  --color-btn-text: #0e141a;
  --color-btn-hover-text: #fff;
  --color-logo-glow: #10bfff3c;
}

/* --------------------------
   RESET & BASE
-------------------------- */
* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  background: var(--color-bg);
  color: var(--color-headline);
  font-family: 'Inter', Arial, sans-serif;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background 0.3s, color 0.3s;
}
section, header { scroll-margin-top: 62px; }

/* --------------------------
   MOBILE NAVBAR
-------------------------- */
.navbar {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: var(--color-nav-bg);
  border-bottom: 1.5px solid var(--color-nav-border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 22px 5vw 18px 5vw;
  box-shadow: 0 2px 20px #0a64cc14;
  backdrop-filter: blur(5px);
}
.nav-title {
  font-family: 'Montserrat', sans-serif;
  font-weight: 700;
  font-size: 1.5rem;
  color: var(--color-accent);
  letter-spacing: 0.04em;
  line-height: 1.1;
}
.navbar-controls {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-left: 25px;
}

/* Nav links default (desktop) */
.nav-links {
  list-style: none;
  display: flex;
  gap: 32px;
  position: static;
  flex-direction: row;
  background: none;
  box-shadow: none;
  border: none;
}
.nav-links li { }
.nav-links li a {
  color: var(--color-headline);
  text-decoration: none;
  font-weight: 700;
  font-size: 1.15rem;
  letter-spacing: 0.01em;
  padding: 7px 6px 7px 6px;
  border-bottom: 2.5px solid transparent;
  transition: color 0.18s, border 0.22s, background 0.16s;
  display: block;
}
.nav-links li a:focus, .nav-links li a:hover, .nav-links li.active a {
  color: var(--color-accent2);
  border-bottom: 2.5px solid var(--color-accent2);
  background: rgba(16,191,255,0.08);
}

/* Theme toggle button */
.theme-toggle-btn {
  border: 1.5px solid #eee;
  background: rgba(255,255,255,0.8);
  border-radius: 2em;
  padding: 7px 19px;
  font-size: 1.33rem;
  color: var(--color-accent);
  cursor: pointer;
  box-shadow: 0 2px 13px #10bfff17;
  transition: background 0.2s, color 0.2s;
  display: flex;
  align-items: center;
  gap: 4px;
  margin: 0;
}
body:not(.light-theme) .theme-toggle-btn {
  background: #bbb;
  border-color: #aaa;
  color: var(--color-accent);
}
.theme-toggle-btn:hover {
  background: var(--color-btn-hover);
  color: var(--color-btn-hover-text);
}

/* Hamburger Styles (hidden on desktop) */
.nav-toggle-btn {
  display: none;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 44px;
  height: 44px;
  background: none;
  border: none;
  cursor: pointer;
  z-index: 1101;
  padding: 0;
}
.burger {
  width: 28px;
  height: 3px;
  background: var(--color-accent2);
  margin: 4px 0;
  border-radius: 2px;
  transition: 0.29s;
  display: block;
}

/* Hamburger transitions to X (when .open on btn) */
.nav-toggle-btn.open .burger:nth-child(1) { transform: translateY(7.5px) rotate(45deg);}
.nav-toggle-btn.open .burger:nth-child(2) { opacity: 0;}
.nav-toggle-btn.open .burger:nth-child(3) { transform: translateY(-7.5px) rotate(-45deg);}

/* MOBILE STYLES */
@media (max-width: 900px) {
  .navbar {
    flex-direction: row;
    flex-wrap: nowrap;
    align-items: center;
    gap: 0;
    padding: 13px 3vw 8px 3vw;
  }
  .nav-title { font-size: 1.23rem; }
  .navbar-controls { margin-left: auto; gap: 8px; }
  .theme-toggle-btn, .nav-toggle-btn { margin: 0; }

  /* Burger visible */
  .nav-toggle-btn { display: flex; }

  /* Mobile nav menu (dropdown) */
  .nav-links {
    position: absolute;
    top: 100%;
    right: 0;
    left: 0;
    background: var(--color-nav-bg);
    flex-direction: column;
    align-items: flex-start;
    gap: 0;
    padding: 16px 0 8px 0;
    z-index: 999;
    border-bottom: 2px solid var(--color-nav-border);
    box-shadow: 0 9px 30px #10bfff16;
    display: none;
    transition: all 0.22s;
  }
  .nav-links.open { display: flex; }
  .nav-links li {
    width: 100%;
    margin: 0;
  }
  .nav-links li a {
    width: 100%;
    text-align: left;
    font-size: 1.13rem;
    font-weight: 700;
    padding: 12px 24px;
    border: none;
    border-bottom: 1px solid #10bfff11;
    background: none;
  }
}
@media (max-width: 540px) {
  .nav-title { font-size: 1.03rem; }
  .navbar { padding: 9px 1vw 7px 1vw; }
  .theme-toggle-btn { font-size: 1.12rem; padding: 6px 12px; }
  .burger { width: 22px; }
}
/* Hide desktop nav menu unless open (on mobile) */
@media (max-width: 900px) {
  .nav-links { display: none; }
  .nav-links.open { display: flex; }
}

/* --------------------------
   HERO SECTION
-------------------------- */
.hero-section {
  width: 100%;
  min-height: 68vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: flex-end;
  padding-top: 2rem;
  padding-bottom: 2.8rem;
  text-align: center;
  background: var(--color-hero-gradient);
}

.hero-logo {
  width: 220px;
  margin-bottom: 18px;
  margin-top: 8px;
  filter: drop-shadow(0 8px 38px var(--color-logo-glow)) drop-shadow(0 1px 24px #1118);
  transition: filter 0.3s;
}

h1 {
  font-family: 'Montserrat', 'Inter', Arial, sans-serif;
  font-weight: 800;
  font-size: 2.6rem;
  margin-bottom: 10px;
  letter-spacing: 0.01em;
  color: var(--color-headline);
}
.tagline {
  color: var(--color-tagline);
  font-size: 1.31rem;
  font-weight: 400;
  margin-bottom: 34px;
  letter-spacing: 0.03em;
  transition: color 0.3s;
}
.cta-btn {
  display: inline-block;
  padding: 17px 44px;
  background: linear-gradient(95deg, var(--color-btn-bg) 60%, var(--color-btn-hover) 100%);
  color: var(--color-btn-text);
  font-family: 'Montserrat', sans-serif;
  font-weight: 700;
  font-size: 1.21rem;
  letter-spacing: 0.025em;
  border-radius: 2em;
  border: none;
  outline: none;
  box-shadow: 0 4px 18px #10bfff30;
  cursor: pointer;
  transition: background 0.18s, color 0.18s, box-shadow 0.19s, transform 0.13s;
  margin-bottom: 26px;
}
.cta-btn:hover, .cta-btn:focus {
  background: var(--color-btn-hover);
  color: var(--color-btn-hover-text);
  box-shadow: 0 0 28px var(--color-btn-hover);
  transform: translateY(-3px) scale(1.04);
}

/* --------------------------
   SECTION/BASE CONTENT
-------------------------- */
section {
  padding: 64px 0 38px 0;
  background: none;
}
.section-content {
  max-width: 1000px;
  margin: 0 auto;
  padding: 0 1.2rem;
}
section h2 {
  font-family: 'Montserrat', sans-serif;
  color: var(--color-headline);
  font-size: 2rem;
  margin-bottom: 18px;
  font-weight: 800;
  text-align: center;
  letter-spacing: 0.02em;
}
section p,
section ul {
  color: var(--color-headline);
  font-size: 1.17rem;
  line-height: 1.7;
  text-align: center;
}
.section-content ul {
  list-style: none;
  margin-top: 12px;
  padding-left: 0;
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.section-content ul li {
  padding: 8px 0;
  border-bottom: 1px solid #2223;
  font-weight: 500;
}
body:not(.light-theme) .section-content ul li { border-bottom: 1px solid #10bfff28; }

/* --------------------------
   ABOUT/WHY BIS SECTION
-------------------------- */
.about-intro {
  font-size: 1.23rem;
  font-weight: 600;
  color: var(--color-accent2);
  text-align: center;
  margin-bottom: 34px;
  margin-top: 0;
  font-family: 'Montserrat', sans-serif;
}
.about-main {
  color: var(--color-headline);
  font-size: 1.13rem;
  line-height: 1.7;
  margin: 0 auto 45px auto;
  max-width: 800px;
}
.about-main p {
  margin-bottom: 14px;
  text-align: center;
}
.why-bis {
  margin: 62px auto 0 auto;
  max-width: 1040px;
  text-align: center;
}
.why-bis h3 {
  color: var(--color-accent2);
  font-size: 1.35rem;
  margin-bottom: 34px;
  font-family: 'Montserrat', sans-serif;
  font-weight: 700;
  letter-spacing: 0.05em;
}
.why-bis-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 36px 30px;
  justify-content: center;
  align-items: stretch;
}
.why-card {
  background: rgba(16,191,255,0.07);
  border: 1.5px solid #10bfff1a;
  border-radius: 15px;
  box-shadow: 0 2px 14px #10bfff10;
  padding: 32px 24px 28px 24px;
  text-align: left;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  transition: box-shadow 0.23s, border 0.19s;
}
.why-card:hover, .why-card:focus-within {
  border: 1.5px solid var(--color-btn-hover);
  box-shadow: 0 2px 28px #10bfff21;
}
.why-icon {
  font-size: 2rem;
  margin-bottom: 13px;
  color: var(--color-accent2);
}
.why-card h4 {
  margin: 0 0 9px 0;
  color: var(--color-accent);
  font-family: 'Montserrat', sans-serif;
  font-size: 1.12rem;
  font-weight: 700;
}
.why-card p {
  color: var(--color-headline);
  font-size: 1.05rem;
  line-height: 1.55;
}
@media (max-width: 700px) {
  .why-bis-grid { grid-template-columns: 1fr; gap: 24px; }
  .why-bis h3 { font-size: 1.16rem; }
}

/* --------------------------
   SERVICES
-------------------------- */
.services-intro {
  font-size: 1.12rem;
  line-height: 1.68;
  color: var(--color-tagline);
  margin-bottom: 32px;
  text-align: center;
}
.services-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 34px 28px;
  margin-bottom: 48px;
}
.service-card {
  background: rgba(16,191,255,0.06);
  border: 1.5px solid #10bfff16;
  border-radius: 15px;
  box-shadow: 0 2px 18px #10bfff11;
  padding: 28px 23px 24px 23px;
  text-align: left;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  transition: box-shadow 0.22s, border 0.17s;
}
.service-card:hover, .service-card:focus-within {
  border: 1.5px solid var(--color-btn-hover);
  box-shadow: 0 2px 28px #10bfff16;
}
.service-icon {
  font-size: 2.1rem;
  margin-bottom: 13px;
  color: var(--color-accent2);
}
.service-card h4 {
  margin: 0 0 7px 0;
  color: var(--color-accent);
  font-size: 1.13rem;
  font-family: 'Montserrat', sans-serif;
  font-weight: 700;
}
.service-card p {
  color: var(--color-headline);
  font-size: 1.04rem;
  line-height: 1.5;
}
.expect-block {
  background: rgba(16,191,255,0.06);
  border: 1.5px solid #10bfff18;
  border-radius: 15px;
  margin-top: 64px;
  padding: 35px 22px 24px 22px;
  box-shadow: 0 2px 17px #10bfff10;
}
.expect-block h3 {
  color: var(--color-accent2);
  font-family: 'Montserrat', sans-serif;
  font-weight: 700;
  font-size: 1.18rem;
  margin-bottom: 21px;
  text-align: center;
  letter-spacing: 0.04em;
}
.expect-list {
  color: var(--color-headline);
  font-size: 1.06rem;
  margin-bottom: 18px;
  list-style-position: inside;
  padding-left: 0;
}
.expect-list li {
  margin-bottom: 12px;
  line-height: 1.5;
}
.expect-assurance {
  color: var(--color-accent);
  text-align: center;
  font-size: 1rem;
  margin-top: 5px;
}

/* --------------------------
   CONTACT FORM
-------------------------- */
.contact-form {
  max-width: 450px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 19px;
  background: rgba(16,191,255,0.045);
  padding: 28px 18px;
  border-radius: 18px;
  box-shadow: 0 2px 20px #10bfff1a;
}
.form-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
}
.contact-form label {
  font-weight: 600;
  color: var(--color-accent);
  font-size: 1.05rem;
  margin-bottom: 2px;
}
.contact-form input, 
.contact-form textarea {
  padding: 11px 15px;
  border: 1.5px solid #10bfff52;
  border-radius: 8px;
  font-family: inherit;
  font-size: 1rem;
  background: var(--color-bg);
  color: var(--color-headline);
  outline: none;
  transition: border 0.2s, background 0.2s;
  box-shadow: 0 1px 8px #10bfff07;
}
.contact-form input:focus, 
.contact-form textarea:focus {
  border-color: var(--color-accent2);
  background: #f1fbff22;
}
.contact-form textarea {
  resize: vertical;
  min-height: 120px;
  max-height: 300px;
}
#form-status {
  margin-top: 10px;
  font-size: 1.05rem;
  text-align: center;
  color: var(--color-accent2);
  min-height: 24px;
}

/* --------------------------
   FOOTER
-------------------------- */
footer {
  width: 100%;
  padding: 22px 0 12px 0;
  color: #8ca6be;
  text-align: center;
  font-size: 1rem;
  letter-spacing: 0.01em;
  background: none;
  margin-top: auto;
}
body:not(.light-theme) footer {
  color: #3ac9f8b8;
}

/* --------------------------
   RESPONSIVENESS
-------------------------- */
@media (max-width: 1200px) {
  .section-content { max-width: 99vw; }
}
@media (max-width: 1000px) {
  .hero-logo { width: 140px; }
  h1 { font-size: 2.2rem; }
}
@media (max-width: 900px) {
  .services-grid, .why-bis-grid { grid-template-columns: 1fr; }
  .section-content { max-width: 100vw; }
}
@media (max-width: 700px) {
  .hero-section { padding-top: 1.3rem; }
  section { padding: 40px 0 23px 0; }
  .hero-logo { margin-top: 4px; }
  .why-bis h3 { font-size: 1.16rem; }
}
@media (max-width: 600px) {
  .section-content, .contact-form { padding: 0 4px; }
  .contact-form { padding: 15px 2px; }
  .services-grid, .why-bis-grid, .expect-block, .why-bis {
    padding-left: 0;
    padding-right: 0;
  }
}
@media (max-width: 420px) {
  .nav-title { font-size: .92rem; }
  .navbar { padding: 7px 1vw; }
  .theme-toggle-btn { font-size: 1rem; padding: 4px 8px; }
}