:root {
    --bg: #000;
    --panel: #0b0b0b;
    --muted: #bfbfbf;
    --accent: #1f8feb;
    --accent-2: #08ffd6;
    --card: #0b0f12;
    --glass: rgba(255,255,255,0.03);
}

* {
    box-sizing: border-box
}

html, body {
    height: 100%;
    margin: 0;
    font-family: Inter,Segoe UI,Arial,sans-serif;
    background: var(--bg);
    color: #fff
}

/* Header */
.site-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 18px;
    background: linear-gradient(180deg, rgba(255,255,255,0.01), transparent);
    border-bottom: 1px solid #0f0f0f
}

.header-left {
    display: flex;
    gap: 12px;
    align-items: center
}

.logo {
    width: 48px;
    height: 48px;
    border-radius: 8px
}

.site-title {
    font-weight: 700;
    font-size: 18px
}

.site-sub {
    font-size: 12px;
    color: var(--muted)
}

.header-right {
}

.about-btn {
    padding: 8px 12px;
    border-radius: 8px;
    background: linear-gradient(90deg,var(--accent),var(--accent-2));
    color: #000;
    font-weight: 700;
    text-decoration: none
}

/* Main */
.main-panel {
    padding: 16px
}

.mini-intro {
    background: linear-gradient(90deg, rgba(31,143,235,0.04), rgba(8,255,214,0.02));
    padding: 12px;
    border-radius: 10px;
    border: 1px solid rgba(31,143,235,0.06);
    color: var(--muted);
    margin-bottom: 12px
}

/* Chat + history layout */
.chat-wrap {
    display: flex;
    gap: 12px;
    max-width: 1200px;
    margin: 0 auto;
    align-items: flex-start
}

.history-panel {
    width: 140px;
    background: #070707;
    border: 1px solid #0f0f0f;
    border-radius: 10px;
    padding: 8px;
    color: var(--muted);
    flex-shrink: 0
}

.history-header {
    font-weight: 700;
    margin-bottom: 6px
}

.history-list {
    max-height: 420px;
    overflow: auto;
    font-size: 13px
}

.small-btn {
    margin-top: 10px;
    padding: 6px 8px;
    border-radius: 8px;
    background: #111;
    border: none;
    color: #fff;
    cursor: pointer
}

/* Chat area */
.chat-area {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 10px
}

.chat-window {
    height: 64vh;
    padding: 16px;
    border-radius: 12px;
    background: #070707;
    border: 1px solid #0f0f0f;
    overflow: auto
}

.msg {
    max-width: 78%;
    padding: 10px 12px;
    border-radius: 14px;
    margin-bottom: 10px;
    line-height: 1.35;
    animation: msgIn .18s ease both
}

    .msg.you {
        margin-left: auto;
        background: linear-gradient(180deg,#0b1320,#07111a);
        border: 1px solid rgba(255,255,255,0.02);
        color: #fff
    }

    .msg.bot {
        margin-right: auto;
        background: linear-gradient(180deg,#071018,#081018);
        border: 1px solid rgba(31,143,235,0.06);
        color: #dbefff;
        box-shadow: 0 6px 20px rgba(31,143,235,0.04)
    }

    .msg .who {
        display: block;
        font-weight: 700;
        margin-bottom: 6px;
        font-size: 13px
    }

/* composer */
.composer {
    display: flex;
    gap: 8px;
    padding: 8px;
    border-radius: 10px;
    background: linear-gradient(180deg, rgba(255,255,255,0.01), transparent);
    border: 1px solid #101010;
    align-items: center
}

    .composer input[type="text"] {
        flex: 1;
        padding: 12px;
        border-radius: 10px;
        background: #070707;
        border: 1px solid #111;
        color: #fff;
        outline: none
    }

.toggle-key {
    background: #111;
    color: var(--accent);
    border: 1px solid rgba(31,143,235,0.15);
    padding: 10px 12px;
    border-radius: 8px;
    cursor: pointer
}

.send-btn {
    background: linear-gradient(90deg,var(--accent),var(--accent-2));
    border: none;
    color: #000;
    padding: 10px 14px;
    border-radius: 9px;
    font-weight: 700;
    cursor: pointer
}

.teacher-btn {
    background: #111;
    border: 1px solid rgba(255,255,255,0.03);
    color: var(--accent);
    padding: 10px 12px;
    border-radius: 8px;
    cursor: pointer
}

/* typing */
.typing {
    display: flex;
    gap: 6px;
    align-items: center;
    margin-left: 6px
}

    .typing .dot {
        width: 8px;
        height: 8px;
        border-radius: 50%;
        background: var(--accent);
        opacity: .2;
        animation: blink 1s infinite
    }

@keyframes blink {
    50% {
        opacity: 1;
        transform: translateY(-4px)
    }
}

/* numeric keyboard */
.hidden {
    display: none !important
}

.numeric-mode {
    max-width: 440px;
    margin: 0 auto
}

.num-display {
    width: 100%;
    padding: 12px;
    border-radius: 8px;
    border: 1px solid rgba(31,143,235,0.12);
    background: #000;
    color: var(--accent);
    text-align: right;
    font-size: 20px;
    margin-bottom: 10px
}

.math-keyboard {
    display: grid;
    grid-template-columns: repeat(4,1fr);
    gap: 8px
}

    .math-keyboard button {
        padding: 14px;
        font-size: 18px;
        border-radius: 10px;
        background: #061018;
        color: var(--accent);
        border: 1px solid rgba(31,143,235,0.06);
        cursor: pointer
    }

    .math-keyboard .back {
        background: #ff5555;
        color: #fff
    }

    .math-keyboard .clear {
        background: #333;
        color: #fff;
        grid-column: span 2
    }

/* About page elements */
.about-container {
    max-width: 900px;
    margin: 18px auto;
    padding: 12px
}

.faq-section .faq-q {
    display: block;
    background: #121212;
    padding: 12px;
    border-radius: 8px;
    border: 1px solid #222;
    margin-top: 10px;
    cursor: pointer;
    color: #e8f6ff
}

.faq-section .faq-a {
    display: none;
    padding: 12px;
    background: #0f1416;
    border-radius: 8px;
    border: 1px solid #222;
    margin-top: 6px;
    color: #cfdce8
}

.share-box {
    margin-top: 12px;
    padding: 12px;
    border-radius: 10px;
    background: #070707;
    border: 1px solid #111
}

.leaderboard-box {
    margin-top: 8px;
    background: #080a0b;
    padding: 10px;
    border-radius: 8px;
    border: 1px solid #111;
    color: var(--muted)
}

/* Footer */
.site-footer {
    padding: 12px 18px;
    text-align: center;
    color: var(--muted);
    border-top: 1px solid #0f0f0f
}

/* Responsive */
@media (max-width:820px) {
    .chat-wrap {
        flex-direction: column
    }

    .history-panel {
        width: 100%;
        order: 2
    }

    .chat-window {
        height: 50vh
    }
}